SHORT PEPTIDES WHICH SELECTIVELY MODULATE INTRACELLULAR SIGNALLING

Abstract: Disclosed are peptides which are peptide derivatives of the HJ loop of a protein tyrosine kinase. The peptides can modulate the activity of the protein tyrosine kinase. Also disclosed are methods of modulating the activity of a protein tyrosine kinase in a subject by administering one of the peptides of the present invention.

Description: SHORT PEPTIDES WHICH SELECTIVELY MODULATE INTRACELLULAR SIGNALLING RELATED PARAGRAPHS This application is a continuation- in-part of U.S. Serial No. 08/861,153, filed on May 21, 1997, the entire teachings of which are incorporated herein by reference. BACKGROUND OF THE INVENTION Protein tyrosine kinases are a member of the eukaryotic protein kinase superfamily. Enzymes of this class specifically phosphorylate tyrosine residues of intracellular proteins and are important in mediating signal transduction in multicellular organisms. Protein tyrosine kinases occur as membrane-bound receptors, which participate in transmembrane signaling, or as intracellular proteins which take part in signal transduction within the cell, including signal transduction to the nucleus. As such, phosphorylation of tyrosine by protein tyrosine kinases is an important mechanism for regulating intracellular events in response to environmental changes. A wide variety of cellular events, including cytokine responses, antigen-dependent immune responses, cellular transformation by RNA viruses, oncogenesis, regulation of the cell cycle and modification of cell morphology and phenotype are regulated by protein tyrosine kinases . Enhanced protein tyrosine kinase activity can lead to persistent stimulation by secreted growth factors which, in turn, can lead to proliferative diseases such as cancer, to nonmalignant proliferative disease such as arteriosclerosis, psoriasis and to inflammatory response such as septic shock. Decreased function can also be lead to disease. For example, a decrease in the activity of insulin receptor tyrosine kinase is a cause of various types of diabetes and severe reduction of the B cell progenitor kinase leads to human X-linked agammaglobulinemia . Thus, there is a need for compounds which can modulate the expression of protein tyrosine kinases. Such compounds have utility in the treatment of diseases caused by over activity or underactivity of protein tyrosine kinases. Such compounds also have utility in studying the mode of action of protein tyrosine kinases and how these proteins regulate cellular functions and activities . SUMMARY OF THE INVENTION It has now been found that short peptides which are derivatives of the HJ loop of a number of different protein tyrosine kinases can significantly affect the activities of cells expressing the protein tyrosine kinase. "HJ loop" is defined hereinbelow. A number of examples are listed below: Peptide derivatives of the HJ loop of c-Src, Csk, c-Abl and c-Met have been found to inhibit the proliferation of a number of a different endothelial cell types (Examples 2 and 4) . Yet other peptide derivatives of the HJ loop of c- Src, Lck and endothelial cells' tyrosine kinase receptors (Endoth) have been found to stimulate the proliferation of bovine capillary endothelial cells in vi tro (Example 2) . Peptide derivatives of the HJ loop of Lyn/Hck have been found to cause morphological changes in vascular smooth muscle cells in vi tro (Example 5) . Specifically, cells incubated with Ac-IVTYGKI-NH 2 (SEQ ID NO.: 1) and Ac-IVTYGRI-NH 2 (SEQ ID NO.: 2), referred to as HJ24 and HJ32, respectively, become elongated and assume a spindle-like structure. Peptide derivatives of the HJ loop of c-Src have been found to protect PC- 12 neuronal cells in vi tro from the effects of serum deprivation (Example 3) . Based on the aforementioned discoveries, novel peptides are disclosed herein which are peptide derivatives of the HJ loop of protein tyrosine kinases. Also disclosed are methods of identifying a peptide derivative of an HJ loop of a protein tyrosine kinase which modulates the activity of said protein tyrosine kinase. Methods of modulating the activity of a protein tyrosine kinase in a subject are also disclosed. One embodiment of the present invention is a novel peptide which is a peptide derivative of the HJ loop of a protein tyrosine kinase. The peptide comprises between about five and about twenty amino acid residues or amino acid residue analogs and modulates the activity of the protein tyrosine kinase. The N-terminus and/or C-terminus of the peptide can be substituted or unsubstituted. The peptide can be linear or cyclic. Another embodiment of the present invention is a method of modulating the activity of a protein tyrosine kinase in a subject. The method comprises administering a therapeutically effective amount of a peptide which is a derivative of an HJ loop of said protein tyrosine kinase, as described above. Yet another embodiment of the present invention is a method of identifying a peptide which modulates the activity of a protein tyrosine kinase. The method comprises providing a "test peptide" which has from about five to about twenty amino acids or amino acid analogs and which is a peptide derivative of the HJ loop of said protein tyrosine kinase. The test peptide is incubated with cells having a cellular activity or function under the control of said protein tyrosine kinase under conditions suitable for assessing the activity of the protein tyrosine kinase. The activity of the protein tyrosine kinase is assessed and compared with cells of the same cell type grown under the same conditions in the absence of the test peptide. A greater or lesser activity compared with cells grown in the absence of the test peptide indicates that the test peptide modulates activity of the protein tyrosine kinase. The peptides of the present invention can be used in the treatment of a wide variety of diseases caused by overactivity and underactivity of a protein tyrosine kinase. Examples include, but are not limited to, cancer, diseases caused by proliferation of smooth muscle (e.g., restinosis and atherosclerosis) psoriasis, inflammatory disorders, diabetes, immune disorders and osteoporosis. The peptides of the present invention also have in vi tro utilities, for example, in the generation of antibodies which specifically bind the protein tyrosine kinase whose HJ loop has a sequence or subsequence corresponding to the peptide. These antibodies can be used to identify cells expressing the protein tyrosine kinase and to study the intracellular distribution of the protein tyrosine kinase. In addition, the peptides can be used to identity and quantitate ligands which bind the HJ loop of the protein tyrosine kinase from which the peptide was derived. BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a sequence illustrating the consensus sequence of the HJ loop found among the family of protein tyrosine kinases . Figure 2 is a Table illustrating the amino acid sequence of the HJ loop of the protein tyrosine kinases c-Src (SEQ ID NO.: 3), Lck (SEQ ID NO.: 4), Csk (SEQ ID NO.: 5), c-Abl (SEQ ID NO . : 6), c- et (SEQ ID NO.: 7) FAK (SEQ ID NO. : 8), Lyn/Hck (SEQ ID NO . : 9), Endoth (SEQ ID NO.: 10) Trk-nerve growth factor (Trk-NGFR) (SEQ ID NO. : 11) , and EGFR (SEQ ID NO. : 12) . Also shown are examples of suitable conservative substitutions in these amino acid sequences. A "*" indicates that the carboxylic acid group in the side chain of the amine acid is protected as an aliphatic, substituted aliphatic, benzylic, substituted benzylic, aromatic or substituted aromatic ester. Figure 3 is a Table illustrating the sequences of the peptides HJ4 (SEQ ID NO.: 13), HJ4.2 (SEQ ID NO.: 14), HJ4Nitro (SEQ ID NO.: 15), HJ6 (SEQ ID NO.: 16), HJ7 (SEQ ID NO.: 17), HJ7.1 (SEQ ID NO.: 18), HJ8 (SEQ ID NO.: 19), HJ9 (SEQ ID NO.: 20), HJ10 (SEQ ID NO.: 21), HJ11 (SEQ ID NO.: 22), HJ11.1 (SEQ ID NO.: 23), HJllMet (SEQ ID NO.: 24), HJ12 (SEQ ID NO.: 25), HJ13 (SEQ ID NO.: 26), HJ14 (SEQ ID NO.: 27), HJ15 (SEQ ID NO.: 28), HJ18 (SEQ ID NO.: 29), HJ20, (SEQ ID NO.: 30), HJ20.1 (SEQ ID NO.: 31), HJ21.1 (SEQ ID NO.: 32), HJ22 (SEQ ID NO.: 33), HJ23.1 (SEQ ID NO.: 34), HJ24 (SEQ ID NO.: 1), HJ25 (SEQ ID NO . : 35), HJ27 (SEQ ID NO . : 36), HJ28 (SEQ ID NO. : 37), HJ30 (SEQ ID NO.: 38), HJ31 (SEQ ID NO.: 39), HJ32 (SEQ ID NO.: 2), HJ33 (SEQ ID NO.: 40), HJ34 (SEQ ID NO.: 41), Lena 1 (SEQ ID NO.: 42), Lena 2 (SEQ ID NO.: 43) and J49 (SEQ ID NO.: 44). Figure 3 also indicates from which protein tyrosine kinase each peptide is derived and to which portion of the HJ loop the sequence of each peptide corresponds. Figure 4 is a graph showing the percent inhibition of proliferation of A19 bovine aortic endothelial cells by increasing concentrations (μM) of K105H101 (SEQ ID NO.: 53) relative to control cells. K105H101 is a peptide derivative of the HJ loop of tyrosine kinase DDR2 . Figure 5 is a graph showing the percent inhibition of proliferation of DU145 prostrate cancer cells by increasing concentrations (μM) of K055H101 (SEQ ID NO. : 72) relative to control cells. K055H101 is a peptide derivative of the HJ loop of tyrosine kinase Lyn . Figure 6 is a graph showing the percent inhibition of proliferation of PC3 prostrate cancer cells by increasing concentrations (μM) of K055H101 (SEQ ID NO. : 72) relative to control cells. K055H101 is a peptide derivative of the HJ loop of tyrosine kinase Lyn . Figure 7 is a Table showing the sequences of exemplary peptide derivatives of the present invention and the tyrosine protein kinases from whose HJ loop they are derived. The peptide derivatives shown in Figure 7 are K061H101 (SEQ ID NO.: 49); K058H101 (SEQ ID NO.: 50) , K104H001 (SEQ ID NO. : 51 ) ; K104H101 (SEC ID NO 52 ) ; K105H101 (SEQ ID NO. : 53) ; K105H102 (SEC ) ID NO 54) , K105H103 ( SEQ ID NO. : 55) , K105H104 ( SEQ ID NO. 56) , K105H105 ( SEQ ID NO. : 57), K105H106 ( SEQ ID NO. 58) , K077H101 ( SEQ ID NO. : 59) , K078H101 ( SEQ ID NO. 60) , K078H102 ( SEQ ID NO. : 61 ) ; K066H101 (SEQ ID NO 62) , K060H101 SEQ ID NO. : 63) , K073H101 SEQ ID NO. 64) , K074H101 ( SEQ ID NO. : 65) , K075H101 SEQ ID NO. 66) K094H101 SEQ ID NO. : 67) , K094H102 SEQ ID NO. 68) K057H101 SEQ ID NO. : 69) K056H101 SEQ ID NO. 70) K055H101 SEQ ID NO. : 71) K055H104 SEQ ID NO. 72) K055H111 SEQ ID NO. : 73) K055H112 SEQ ID NO. 74) K055H115 SEQ ID NO. : 75) K055H116 SEQ ID NO. 76) • K055H117 SEQ ID NO. : 77) • K055H118 ISEQ ID NO. 78) ■ K055H119 SEQ ID NO. : 79) K055H120 SEQ ID NO. 80) ■ K055H901 SEQ ID NO. : 81) • K055H902 (SEQ ID NO. 82) • K055H903 SEQ ID NO. : 83) K055H904 (SEQ ID NO. 84) • K109H101 SEQ ID NO. : 85) ■ K080H001 (SEQ ID NO. 86) • K080H002 'SEQ ID NO. : 87) • K080H101 (SEQ ID NO. 88) ■ K051H102 SEQ ID NO. : 89) • K051H103 (SEQ ID NO. 90) • K082H001 (SEQ ID NO. : 91) ■ K083H101 (SEQ ID NO. 92) • K083H102 (SEQ ID NO. : 93 ; ; K081H101 (SEQ ID NO 94) - K081H102 (SEQ ID NO. : 95) • K084H101 (SEQ ID NO. 96) ; K084H102 (SEQ ID NO. : 97) ; K085H101 (SEQ ID NO. 98); K086H101 (SEQ ID NO.: 99); K086H102 (SEQ ID NO.: 100); K108H101 (SEQ ID NO.: 101). DETAILED DESCRIPTION OF THE INVENTION A protein tyrosine kinase (hereinafter "PTK") is a membrane bound or intracellular protein which uses the gamma phosphate of ATP or GTP to generate phosphate monoesters on the phenolic group of a tyrosine residue. PTKs have homologous "kinase domains" or "catalytic domains" which carry out this phosphorylation. Based on a comparison of a large number of protein kinases, it is now known that the kinase domain of protein kinases, including PTKs, can be divided into twelve subdomains, which are regions generally uninterrupted by large amino acid insertions and contain characteristic patterns of conserved residues (Hanks and Hunter, "The Eukaryotic Protein Kinase Superfamily" , in Hardie and Hanks (ed.), The Protein Kinase Facts Book, Volume I, Academic Press, Chapter 2, 1995. These subdomains are referred to as Subdomain I through Subdomain XII. The "HJ loop" referred to herein is found within the kinase domain of PTKs between the middle of Subdomain IX and the middle of Subdomain X. Because of the high degree of homology found in the subdomains of different protein kinases, including PTKs, the amino acid sequences of the domains of different PTKs can be aligned. Thus, the HJ loop of a PTK can be defined by reference to the amino acid sequence of a prototypical protein kinase, for example PKA-Cα, and can be said to correspond to a contiguous sequence of about twenty amino acid residues found between about amino acid 229 and 248 of PKA-Cα. A second definition of the HJ loop of a PTK, which is complementary to the definition provided in the proceeding paragraph, can be made by reference to the three dimensional structure of the kinase domain of PTKs . The kinase domain of PTKs has been found to contain at least nine alpha helices, referred to as helix A through helix I (Tabor et al . , Phil . Trans . R. Soc . Lond . 5340:315 (1993), Mohammadi et al . , Cell 86 : 511 (1996) and Hubbard et al . , Na ture 372 : 146 (1994)) . The HJ loop is a contiguous sequence of about twenty amino acids beginning within the F helix about five amino acids residues from the N-terminus of the F helix and extending about five amino acid residues into the G helix. Optionally, the C-terminus or the N-terminus of the peptides of the present invention, or both, can be substituted with a carboxylic acid protecting group or an amine protecting group, respectively. Suitable protecting groups are described in Green and Wuts, "Protecting Groups in Organic Synthesis ", John Wiley and Sons, Chapters 5 and 7, 1991, the teachings of which are incorporated herein by reference. Preferred protecting groups are those which facilitate transport of the peptide into a cell, for example, by reducing the hydrophilicity and increasing the lipophilicity of the peptide. Examples of N-terminal protecting groups include acyl groups (-C0-R..) and alkoxy carbonyl or aryloxy carbonyl groups (-C0-0-R , wherein R 1 is an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or a substituted aromatic group. Specific examples of acyl groups include acetyl, (ethyl) -CO-, n-propyl-CO- , iso-propyl-CO- , n-butyl-CO- , sec-butyl -CO- , t-butyl-CO- , phenyl-CO-, substituted phenyl-CO-, benzyl-CO- and (substituted benzyl) -CO-. Examples of alkoxy carbonyl and aryloxy carbonyl groups include CH 3 -0-C0-, (ethyl) -0-CO- , n-propyl-O-CO- , isopropyl-O-CO- , n-butyl-O-CO-, sec-butyl-O-CO- , t-butyl-0- C0-, phenyl-O-CO- , substituted phenyl -O-CO- and benzyl- 0-CO-, (substituted benzyl) -O-CO- . The carboxyl group at the C-terminus can be protected, for example, as an an amide (i.e., the hydroxyl group at the C-terminus is replaced with -NH 2 , -NHR 2 and -NR 2 R 3 ) or ester (i.e. the hydroxyl group at the C-terminus is replace with -OR 2 ) . R 2 and R 3 are independently an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aryl or a substituted aryl group. In addition, taken together with the nitrogen atom, R 2 and R 3 can form a C4 to C8 heterocyclic ring with from about 0-2 additional heteroatoms such as nitrogen, oxygen or sulfur. Examples of suitable heterocyclic rings include piperidinyl , pyrrolidinyl , morpholino, thiomorpholino or piperazinyl . Examples of C-terminal protecting groups include -NH 2 , -NHCH 3 , -N(CH 3 ) 2 , -NH(ethyl), -N(ethyl) 2 , - N (methyl) (ethyl) , -NH(benzyl), -N(C1-C4 alkyl) (benzyl) , -NH(phenyl), -N(C1-C4 alkyl) (phenyl) , -OCH 3 , -O- (ethyl) , -0- (n-propyl) , -0- (n-butyl) , -0- (iso-propyl) , -0- ( sec- butyl), -0- ( t-butyl) , -0-benzyl and -0-phenyl . A "peptide derivative of the HJ loop" includes a peptide having the amino acid sequence of the HJ loop. A "peptide derivative of the HJ loop" also includes, for example, a subsequence of the HJ loop of the PTK. A subsequence is a contiguous sequence of from about five to about twenty amino acids found within a larger sequence. Thus, a subsequence of the HJ loop is a contiguous sequence of from about five to about twenty amino acids found within the HJ loop. A subsequence of the HJ loop can also be referred to as a "fragment" of the HJ loop . A "peptide derivative" also includes a peptide having a "modified sequence" in which one or more amino acids in the original sequence or subsequence have been substituted with a naturally occurring amino acid or amino acid analog (also referred to as a "modified amino acid") . In one aspect of the present invention, the peptide derivative has a sequence corresponding to a subsequence of the HJ loop of a PTK, with the proviso that any one amino acid residues in the peptide derivative can differ from the corresponding amino acid residue in the subsequence. For example, if the subsequence is [AAJ - [AA 2 ] -AA 3 ] - [AA 4 ] - [AA 5 ] , then the peptide derivative can be [ΑA 1 ' ] - [AA 2 ] - [AA 3 ] - [AAJ - [AA 5 ] , [AAJ - [AA 2 ' ] - [AA 3 ] - [AAJ - [AA 5 ] , [AAJ - [AA 2 ] - [AA 3 ' ] - [AAJ - [AAJ , [AAJ - [AAJ - [AAJ - [AA 4 ' ] - [AAJ and [AAJ - [AAJ -AAJ - [AAJ - [AA 5 ' ] , wherein [AA' ] is a naturally occurring or modified amino acid different from [AA] . In another aspect of the present invention, the peptide derivative has a sequence corresponding to a subsequence of the HJ loop of a PTK, with the proviso that any two amino acid residues in the peptide derivative can differ from the corresponding amino acid residue in the subsequence. An "amino acid residue" is a moiety found within a peptide and is represented by -NH-CHR-C0-, wherein R is the side chain of a naturally occurring amino acid. When referring to a moiety found within a peptide, the terms "amino acid residue" and "amino acid" are used interchangeably in this application. An "amino acid residue analog" includes D or L residues having following formula: -NH-CHR-CO-, wherein R is an aliphatic group, a substituted aliphatic group, a benzyl group, a substituted benzyl group, an aromatic group or a substituted aromatic group and wherein R does not correspond to the side chain of a naturally-occurring amino acid. When referring to a moiety found within a peptide, the terms "amino acid residue analog" and "amino acid analog" are used interchangeably in this application. As used herein, aliphatic groups include straight chained, branched or cyclic C1-C6 hydrocarbons which are completely saturated, which contain one or two heteroatoms such as nitrogen, oxygen or sulfur and/or which contain one or more units of unsaturation. Aromatic groups include carbocyclic aromatic groups such as phenyl and naphthyl and heterocyclic aromatic groups such as imidazolyl, indolyl, thienyl, furanyl , pyridyl, pyranyl, pyranyl , oxazolyl, benzothienyl , benzofuranyl , quinolinyl, isoquinolinyl and acridintyl . Suitable substituents on an aliphatic, aromatic or benzyl group include, for example, -OH, halogen (-Br, - Cl, -I and -F) -0 (aliphatic, substituted aliphatic, benzyl, substituted benzyl, aryl or substituted aryl group), -CN, -N0 2 , -COOH, -NH 2 , -NH (aliphatic group, substituted aliphatic, benzyl, substituted benzyl, aryl or substituted aryl group), -N(aliphatic group, substituted aliphatic, benzyl, substituted benzyl, aryl or substituted aryl group) 2 , -COO (aliphatic group, substituted aliphatic, benzyl, substituted benzyl, aryl or substituted aryl group), -CONH 2 , -CONH (aliphatic, substituted aliphatic group, benzyl, substituted benzyl, aryl or substituted aryl group)), -SH, -S (aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic group) and -NH-C (=NH) - NH 2 . A substituted benzylic or aromatic group can also have an aliphatic or substituted aliphatic group as a substituent. A substituted aliphatic group can also have a benzyl, substituted benzyl, aryl or substituted aryl group as a substituent. A substituted aliphatic, substituted aromatic or substituted benzyl group can have more than one substituent. Suitable substitutions for amino acid residues in the sequence of an HJ loop or a subsequence of an HJ loop include conservative substitutions which result in peptide derivatives which modulate the activity of a PTK. A conservative substitution is a substitution in which the substituting amino acid (naturally occurring or modified) has about the same size and electronic properties as the amino acid being substituted. Thus, the substituting amino acid would have the same or a similar functional group in the side chain as the original amino acid. A "conservative substitution" also refers to utilizing a substituting amino acid which is identical to the amino acid being substituted except that a functional group in the side chain is functionalized with a suitable protecting group. Suitable protecting groups are described in Green and Wuts, "Protecting Groups in Organic Synthesis " , John Wiley and Sons, Chapters 5 and 7, 1991, the teachings of which are incorporated herein by reference. As with N-terminal and C-terminal protecting group, preferred protecting groups are those which facilitate transport of the peptide into a cell, for example, by reducing the hydrophilicity and increasing the lipophilicity of the peptide, and which can be cleaved, either by hydrolysis or enzymatically, inside the cell (Ditter et al . , J. Pharm . Sci . 57:783 (1968); Ditter et al . , J. Pharm . Sci . 57:828 (1968); Ditter et al . , J. Pharm . Sci . 58:557 (1969); King et al . , Biochemi stry 26 : 2294 (1987); Lindberg et al . , Drug Metabolism and Disposi tion 17:311 (1989); Tunek et al . , Biochem . Pharm . 37:3867 (1988), Anderson et al . , Arch . Biochem . Biophys . 239 : 538 (1985) and Singhal et al . , FASEB J. 1:220 (1987)). Suitable hydroxyl protecting groups include ester, carbonate and carbamate protecting groups. Suitable amine protecting groups include acyl groups and alkoxy or aryloxy carbonyl groups, as described above for N-terminal protecting groups. Suitable carboxylic acid protecting groups include aliphatic, benzyl and aryl esters esters, as described above for C-terminal protecting groups. In one embodiment, the carboxylic acid group in the side chain of one or more glutamic acid or aspartic acid residues in a peptide of the present invention is protected, preferably as a methyl, ethyl, benzyl or substituted benzyl ester, more preferably as a benzyl ester. Provided below are groups of naturally occurring and modified amino acids in which each amino acid in a group has similar electronic and steric properties. Thus, a conservative substitution can be made by substituting an amino acid with another amino acid from the same group. It is to be understood that these groups are non-limiting, i.e. that there are additional modified amino acids which could be included in each group . Group I includes leucine, isoleucine, valine, methionine, serine, cysteine, threonine and modified amino acids having the following side chains: ethyl, n-butyl, -CH 2 CH 2 OH, -CH 2 CH 2 CH 2 OH, - CH 2 CHOHCH 3 and -CH 2 SCH 3 . Preferably, Group I includes leucine, isoleucine, valine and methionine . Group II includes glycine, alanine, valine, serine, cysteine, threonine and a modified amino acid having an ethyl side chain. Preferably, Group II includes glycine and alanine. Group III includes phenylalanine, phenylglycine, tyrosine, tryptophan, cyclohexylmethyl , and modified amino residues having substituted benzyl or phenyl side chains. Preferred substituents include one or more of the following: halogen, methyl, ethyl, nitro, -NH 2 , methoxy, ethoxy and -CN. Preferably, Group III includes phenylalanine, tyrosine and tryptophan. Group IV includes glutamic acid, aspartic acid, a substituted or unsubstituted aliphatic, aromatic or benzylic ester of glutamic or aspartic acid (e.g., methyl, ethyl, n-propyl iso-propyl, cyclohexyl, benzyl or substituted benzyl), glutamine, asparagine, CO-NH-alkylated glutamine or asparagine (e.g., methyl, ethyl, n-propyl and isopropyl) and modified amino acids having the side chain - (CH 2 ) 3 -COOH, an ester thereof (substituted or unsubstituted aliphatic, aromatic or benzylic ester) , an amide thereof and a substituted or unsubstituted N-alkylated amide thereof. Preferably, Group IV includes glutamic acid, aspartic acid, methyl aspartate, ethyl aspartate, benzyl aspartate and methyl glutamate, ethyl glutamate and benzyl glutamate. Group V includes histidine, lysine, arginine, N- nitroarginine, β-cycloarginine, γ-hydroxyarginine, N-amidinocitruline and 2-amino-4-guanidinobutanoic acid, homologs of lysine, homologs of arginine and homologs of ornithine. Preferably, Group V includes histidine, lysine, arginine and ornithine. A homolog of an amino acid includes from 1 to about 3 additional methylene units in the side chain. Group VI includes serine, theronine, cysteine and modified amino acids having C1-C5 straight or branched alkyl side chains substituted with -OH or -SH. Preferably, Group VI includes serine, cysteine or threonine. In another aspect, suitable substitutions for amino acid residues in the sequence of an HJ loop or a subsequence of an HJ loop include "severe" substitutions which result in peptide derivatives which modulate the activity of a PTK. Severe substitutions which result in peptide derivatives that modulate the activity of a PTK are much more likely to be possible in positions which are not highly conserved throughout the family of protein tyrosine kinases than at positions which are highly conserved. Figure 1 shows the consensus sequence of the about 20 amino acids of HJ loop. Positions which are highly conserved among the PTK family and the conserved amino acids generally found in those positions have been indicated. Positions which are not as highly conserved among the PTK family of proteins have been left blank. A "severe substitution" is a substitution in which the substituting amino acid (naturally occurring or modified) has significantly different size and/or electronic properties compared with the amino acid being substituted. Thus, the side chain of the substituting amino acid can be significantly larger (or smaller) than the side chain of the amino acid being substituted and/or can have functional groups with significantly different electronic properties than the amino acid being substituted. Examples of severe substitutions of this type include the substitution of phenylalanine or cycohexylmethyl glycine for alanine, isoleucine for glycine, a D amino acid for the corresponding L amino acid or -NH-CH [ ( -CH 2 ) 5 -C00H] -CO- for aspartic acid. Alternatively, a functional group may be added to the side chain, deleted from the side chain or exchanged with another functional group. Examples of severe substitutions of this type include adding an amine or hydroxyl, carboxylic acid to the aliphatic side chain of valine, leucine or isoleucine, exchanging the carboxylic acid in the side chain of aspartic acid or glutamic acid with an amine or deleting the amine group in the side chain of lysine or ornithine. In yet another alternative, the side chain of the substituting amino acid can have significantly different steric and electronic properties that the functional group of the amino acid being substituted. Examples of such modifications include tryptophan for glycine, lysine for aspartic acid and ~(CH 2 ) 4 COOH for the side chain of serine. These examples are not meant to be limiting. Another example of a suitable severe substitution is the replacement of conserved glycine residues (e.g., positions seven and thirteen in Figure 1) with D- configuration amino acids or analogs thereof, which have a hydrogen atom at a position identical to the glycine hydrogen side-chain. J49 is an example of a peptide with such a severe substitution (D-lysine for conserved glycine) . Examples PTKs of whose activity can be modulated by peptide and peptide derivatives, as described herein, include, but are not limited to, PTKs belonging to the following PTK families: Src, EGF-R, FGF-R, VEGF-R, HGF- R, PDGF-R, the insulin receptor family and the neurotrophin receptor family. Suitable members of the Src family include, but are not limited to, c- Src, c- Yes, FYN, FGR, HCK, LYN, LCK and BLK. Suitable members of the EGF-R family include, but are not limited to EGFR, ErbB2, ErbB3 and ErbB4. Suitable members of the FGF-R family include, but are not limited to FGFR1 , FGFR2, FGFR3 and FGFR . Suitable members of the VEGF-R family include, but are not limited to, Fltl, Flt4 and Flkl . Suitable members of the insulin receptor family include, but are not limited to, INS-R, IRR and IGF1-R. Other suitable PTKs include, but are not limited to, RET, CSK, c-Met, c-Abl and FAK. The present invention includes peptides having amino acids sequences corresponding to the sequence found in the HJ loop of PTKs, subsequences thereof and modified subsequences thereof. Examples of suitable subsequences include, but are not limited to, sequences corresponding to [AA] 1 through [AA] 20 , [AA] 3 through [AA] 10 [AA] 7 through [AA] 14 _ [AA] l through [AA] 18 , [AA] 3 through [AA] 14 , [AA] 7 through [AA] 18 and [AA] 3 through [AA] 18 of the HJ loop of a PTK, and subsequences thereof. Figure 2 shows the sequences of the HJ loop of the following PTKs: c-Src, Lck, Csk, c-Abl, c-Met, FAK, Lyn/Hck, Endoth and Trk-NGFR. Figure 2 also provides a numbering scheme for the amino acid sequence in an HJ loop. The amino acid at the N-terminus of the HJ loop is at position 1 and can be referred to as " [AA] J 1 . The next amino acid in the sequence, referred to as "[AA] 2 ", is at position 2 and is followed by amino acids [AA] 3 through [AA] 20 , which are at positions 3-20. Thus, a peptide 20-mer with an amino acid sequence [AA] . through [AA] 20 includes the twenty amino acids in the HJ loop. A peptide derivative of the HJ loop with an amino acid sequence [AA] 3 through [AA] 10 , as recited in the preceeding paragraph, includes the third amino acid through the tenth amino acid in said HJ loop. The present invention also includes peptides having amino acids sequences corresponding to a modified sequence or subsequence of the HJ loop of PTKs and which modulate the activity of PTKs. In one aspect, one, two or more of the amino acids in the sequence or subsequence are modified with conservative substitutions; the substitutions can be in consensus positions, in non-consensus positions or in both. Figure 2 also provides examples of suitable conservative amino acid substitutions for the HJ loop of c-Src, Lyn/Hck, Lck, Csk, c-Abl, c-Met, FAK, Endoth and nerve growth factor (Trk-NGFR) . In another aspect, one, two or more of the amino acids in the sequence or subsequence are modified with severe substitutions; the substitutions are preferably in non-consensus positions. Specific examples of peptide derivatives of the present invention include peptides shown in Figure 3. The N-terminus and/or C-terminus of these peptides can be modified, as described above. As indicated in Figure 3, the N-terminal of these peptides is typically acetylated and the C-terminal is typically amidated. Other protecting groups for amides and carboxylic can be used, as described above. Optionally, one or both protecting groups can be omitted. The peptides may by cyclic or linear. Also included are peptides shown in Figure 3 with the proviso that any one of the amino residues in the peptide can vary, being any naturally occurring amino acid or analog thereof. The present invention also includes the peptides shown in Figure 3 with the proviso that any two of the amino residues in the peptide can vary, being any naturally occurring amino acid or analog thereof . Other specific examples of a peptide included within the present invention is a peptide having the sequence Leu-Val-Thr-Xaa-Gly-Arg-Val (SEQ ID NO . : 45) or Gly-Arg-Val-Pro-Yaa-Pro-Zaa (SEQ ID NO. : 46) . The N- terminus and/or the C-terminus can optionally be protected, for example, N-acetylated and/or C-amidated. Xaa is selected from the group consisting of L-lysine, D-lysine, histidine, tyrosine, phenylalanine and arginine; Yaa is selected from the group consisting of tyrosine, phenylalanine and tryptophane; Zaa is selected from the group consisting of glycine, alanine and arginine . The present invention also includes cyclic peptides having amino acids sequences corresponding to a modified sequence or subsequence of the HJ loop of PTKs and which modulate the activity of PTKs. A "cyclic peptide" refers, for example, to a peptide or a peptide or peptide derivative in which a ring is formed by a peptide bond between the nitrogen atom at the N-terminus and the carbonyl carbon at the C-terminus. "Cyclized" also refers to forming a ring by a covalent bond between the nitrogen at the N-terminus of the compound and the side chain of a suitable amino acid in the peptide, preferably the C-terminal amino acid. For example, an amide can be formed between the nitrogen atom at the N-terminus and the carbonyl carbon in the side chain of aspartic acid or glutamic acid. Alternatively, the peptide or peptide derivative can be cyclized by forming a covalent bond between the carbonyl at the C-terminus of the compound and the side chain of a suitable amino acid in the peptide, preferably the N- terminal amino acid. For example, an amide can be formed between the carbonyl carbon at the C-terminus and the amino nitrogen atom in the side chain of lysine or ornithine; an ester can be formed between the carbonyl carbon at the C-terminus and the hydroxyl oxygen atom in the side chain of serine or threonine. "Cyclized" also refers to forming a ring by a covalent bond between the side chains of two suitable amino acids in the peptide, preferably the terminal amino acids. For example, a disulfide can be formed between the sulfur atoms in the side chains of two cysteines . Alternatively, an ester can be formed between the carbonyl carbon in the side chain of, for example, glutamic acid or aspartic acid, and the oxygen atom in the side chain of, for example, serine or threonine. An amide can be formed between the carbonyl carbon in the side chain of, for example, glutamic acid or aspartic acid, and the amino nitrogen in side chain of, for example, lysine or ornithine. In addition, a peptide or peptide derivative can be cyclized with a linking group between the two termini, between one terminus and the side chain of an amino acid in the peptide or peptide derivative, or between the side chains to two amino acids in the peptide or peptide derivative. Suitable linking groups are disclosed in Lobl et al . , WO 92/00995 and Chiang et al . , WO 94/15958, the teachings of which are incorporated into this application by reference. Suitable substitutions in the original amino acid sequence or subsequence are those which result in a peptide derivative, as defined above, which modulates the activity of a PTK. The activity of a PTK is "modulated" when the activity of the PTK is increased or decreased. An increase or decrease in the activity of a PTK can be detected by a corresponding modulation, increase or decrease, in a cellular activity or function which is under the control of the PTK. Examples of these cellular functions include cell proliferation, cell differentiation, cell morphology or gene expression. It can be readily determined whether a peptide or peptide derivative modulates the activity of a PTK by obtaining cells which have one or more cellular activities controlled by a PTK. The cells are incubated with the peptide or peptide derivative to produce a test mixture under conditions suitable for assessing activity of the protein tyrosine kinase. The activity of the PTK is assessed and compared with a suitable control, e.g., the activity of the same cells incubated under the same conditions in the absence of the peptide or peptide derivative. A greater or lesser activity of the PTK in the test mixture compared with the control indicates that the test peptide or peptide derivative modulates the activity of said PTK. Suitable cells for the assay include normal cells which express a membrane bound or intracellular PTK, transformed cells or cells which have been genetically engineered to express a PTK. Other suitable cells include cancer cells, which can be assayed for proliferation and differentiation; for example, Src, Csk and Fak are related to a whole spectrum of malignant cells. In addition, specific tumors with their corresponding involved Ptks can be used, including breast and ovarian cancer cells (EGFR) , prostrate cancer cells (FGF) , leukemia cells (Abl) hepatoma cells (Met) . Vascular smooth muscle cells can be assayed for proliferation and migration (FGFRs and PDGFRs) . Cells of the immune system can be assayed for cytokine production such as IL-2, TNF and INF (Lyn, Hck, Blk and Lck) . Osteoclasts can be assayed for bone resorption (Src and Csk) . Neuronal cells can be assayed for differentiation (Trks) . Epithelial tissues such as epidermis, intestinal epithelium and breast can be assayed for proliferation, differentiation and regeneration (EGFRs) . Liver cells can be assayed for proliferation, differentiation and regeneration (c-Met) . Endothelial cells can be assayed for proliferation and migration (VEGFRs, FGFRs and c-Met) . Conditions suitable for assessing PTK activity include conditions suitable for assessing activity of a cellular activity or function under control of the PTK. Generally, a cellular activity or function can be assessed when the cells are exposed to conditions suitable for cell growth, including a suitable temperature (for example, between about 30 °C to about 42 °C) and the presence of the suitable concentrations of nutrients in the medium (e.g., amino acids, vitamins, growth factors, etc.) . Conditions suitable for cell growth are used when the cellular activity or function being assessed is, for example, cell proliferation, differentiation, cell morphology, gene expression, cell survival, cell response to external stimuli and cell phenotype . In another aspect, the activity of a PTK can be evaluated by growing the cells under serum deprivation conditions. Cells are typically grown in culture in the presence of a serum such as bovine serum, horse serum or fetal calf serum. Many cells, for example, nerve cells such as PC-12 cells, generally do not survive when insufficient serum. The use of insufficient serum in the growth medium to culture cells is referred to as "serum deprivation conditions" and includes, for example, from 0% to about 4% serum. Nerve growth factor (NGF) can protect PC-12 and other nerve cells from the effects of serum deprivation conditions. PTK activity is determined by the extent to which a peptide or peptide derivative can protect cells, e.g., neuronal cells, from the consequences of serum deprivation. Specific conditions are provided in Example 3. Generally, the activity of the PTK in the test mixture is assessed by making a quantitative measure of the cellular activity which the PTK controls. For example, if cells are being used in which the PTK controls cell proliferation (e.g., bovine endothelial capillary cells in the presence of basic fibroblast growth factor) , then PTK activity is assessed by measuring cellular proliferation, for example, by comparing the number cells present after a given period of time with the number of cells originally present. If cells are being used in which the PTK controls cell differentiation (e.g., PC-12 cells transfected with c- Src, see Alema et al . , Nature 316 : 551 (1985)), activity is assessed by measuring the degree of differentiation (e.g., the degree to which neurites are extended and the degree to which markers of neuronal differentiation are expressed in PC-12 cells transfected with c-Src ; see Alema et al . , and the degree to which the formation of mesoderm in developing Xenopus embroya cells is induced; see Burgess and Maciag, Ann . Rev. Biochem . , 58 : 515 (1989) and Dionne et al . , WO 92/00999) . Activity can also be assessed by the extent to which the gene expression, cell morphology or cellular phenotype is altered, e.g., by assessing the degree to which cell shape is altered, the degree to which the cells assume a spindle-like structure, alleration in gene expression or a change in the response to external stimuli (see Example 5 for conditions suitable for assessing changes in cell shape) . If serum deprivation conditions are used, then activity is assessed by the extent of cell survival. Greater cell survival in the test mixture compared with the control indicates that peptide or peptide derivative is able to prevent apoptosis (programed cell death) . Specific examples of conditions suitable for determining the activity of PTKs by assessing cell proliferation are provided in Examples 2 and 4. Specific examples of serum deprivation conditions suitable for determining the activity of PTKs by assessing cell survival are provided in Example 3. It is to be understood that the assay described hereinabove for determining whether a peptide or peptide derivative modulates a cellular activity or function under the control of a PTK can be performed with cells other than those specifically described herein. PTKs not yet discovered or PTKs whose function is not yet known can also be used in this assay, once it has been determined which cellular functions or activities they control . These PTKs are also within the scope of the present invention. The present invention is also directed to a method of modulating the activity of a protein tyrosine kinase in a subject. A "subject" is preferably a human, but can also be an animal in need of treatment, e.g., veterinary animals (e.g., dogs, cats, and the like), farm animals (e.g., cows, pigs, horses and the like) and laboratory animals (e.g., rats, mice, guinea pigs and the like) . The activity of a PTK in a subject can be modulated for the purpose of treating certain diseases, for example, proliferative diseases such as cancer, nonmalignant proliferative disease such as arteriosclerosis, psoriasis and inflammatory responses such as septic shock. For example, cancer can be treated by anti-angiogenic therapies. Inhibition of c- Met or tyrosine kinase receptors which respond to fibroblast growth factor (FGF) , or vascular endothelial growth factor (VEGF) decreases angiogenesis . As a result, cancers can be treated by administering a therapeutically effective amount of a peptide or peptide derivative which results in decreased activity of c-Met or tyrosine kinase receptors which respond to FGF or VEGF. In addition, RET is involved in certain thyroid cancers; therapeutically effective amounts of peptides or peptide derivatives which modulate the activity of RET can be used to treat these thyroid cancers . Restenosis is caused by vascular smooth muscle proliferation in response to, for example, vascular injury caused by balloon catheterization. Vascular smooth muscle proliferation is also a cause of arteriosclerosis. Vascular smooth muscle proliferation is a result of, for example, inhibition of Csk and/or stimulation of tyrosine kinase receptors which respond to FGF or platelet derived growth factor (PDGF) . Thus, restenosis and arteriosclerosis can be treated with a therapeutically effective amount of a peptide or peptide derivative which inhibits tyrosine kinase receptors which respond to FGF or PDGF or which activate Csk. FGF has also been imlpicated in psoriasis, arthritis and benign prostatic hypertrophy (Dionne et al . , WO 92/00999). These conditions can be treated with HJ peptides from PTKs which respond to FGF. Src activity is responsible, at least in part, for bone resorption. Thus, osteoporosis can be treated with a therapeutically effective amount of a peptide or peptide derivative which inhibits Src activity or which activates Csk. Lyn and Hck are activated during the non-specific immune response which occurs in individuals with arthritis which occurs in individuals as a result of allergic responses. Lyn is also activated in individuals with septic shock. Thus, these conditions can be treated with a therapeutically effective amount of a peptide or peptide derivative which inhibits the activity of these PTKs. Lck is expressed in T cells and is activated during a T cell immune response. Similarly, Lyn is expressed in B cells and activated during a B cell immune response. Thus, conditions which are caused by overactivation of T cells or B cells can be treated by administering a therapeutically effective amount of a peptide or peptide derivative which inhibits Lck or Lyn, respectively. Conditions which are caused by underactivation of T cells or B cells can be treated by administering a therapeutically effective amount of a peptide or peptide derivative which stimulates Lck or Lyn, respectively. In addition, a severe reduction of the B cell progenitor kinase leads to human X- linked agammaglobulinemia, which can be treated by administering a therapeutically effective amount of a peptide or peptide derivative which stimulates B cell progenitor kinase. Decreased function of other PTKs can also be lead to disease. For example, a decrease in the activity of insulin receptor tyrosine kinase (RTK) is a cause of various types of diabetes . These types of diabetes can be treated by administering a therapeutically effective amount of a peptide or peptide derivative which increases the activity of the insulin RTK. Based on methods disclosed herein, peptides and peptide derivatives can be designed to modulate the activity of PTKs whose HJ loop has been sequenced and whose cellular function is known. As a consequence, peptides and peptide derivatives can be designed to affect (increase or decrease) those cellular functions. It is possible that future research will reveal that certain disease conditions, whose underlying causes are presently unknown, are brought about by the overactivity or underactivity of cellular functions controlled by PTKs. These diseases can be treated by administering peptides which are peptide derivatives of the HJ loop of the overactive or underactive PTK. Suitable peptides and peptide derivatives can be identified by methods disclosed herein. These methods of treatment, peptides and peptide derivatives are encompassed within the scope of the present invention. A "therapeutically effective amount" is the quantity of compound which results in an improved clinical outcome as a result of the treatment compared with a typical clinical outcome in the absence of the treatment. An "improved clinical outcome" refers, for, example, to a longer live expectancy, fewer complications, fewer symptoms, less physical discomfort and/or fewer hospitalizations as a result of the treatment . With respect to cancer, an "improved clinical outcome" includes a longer life expectancy. It can also include slowing or arresting the rate of growth of a tumor, causing a shrinkage in the size of the tumor, a decreased rate of metastasis or an improved quality of life (e.g., a decrease in physical discomfort or an increase in mobility) . With respect to restenosis and arteriosclerosis, "an improved clinical outcome" includes, for example, a longer life expectancy or a decrease in the rate of arterial occlusion. It can also include an improved quality of life (e.g., a decrease in physical discomfort, an increase in mobility and a decrease in the frequency and/or length of hospitalization) . With respect to osteoporosis, "an improved clinical outcome" includes, for example, a decrease in the rate of bone deterioration, an increase in the rate of bone formation and/or an improved quality of life (e.g., a decrease in physical discomfort, an increase in mobility and a decrease in the frequency and/or length of hospitalization) . With respect to modulation of the immune system, "an improved clinical outcome" refers to an increase in the magnitude of the immune response in the individual, if the individual has a disease involving immune suppression. For example, for individuals with x-linked agammaglobulinemia, an improved clinical outcome includes an increase in the immunoglobulin level. "An improved clinical outcome" for individuals with suppressed immune systems can also refer to a lesser susceptibility to infectious diseases. For diseases involving an overactive immune system, "an improved clinical outcome" refers to a decrease in the magnitude of the immune response. In both cases, "an imporved clinical outcome can also involve an improvement in the quality of life, as described above. With respect to diabetes, an improved clinical outcome refers to a longer life expectancy, a reduction in the complications of the disease (e.g., neuropathy, retinopathy, nephropathy and degeneration of blood vessels) and an improved quality of life, as described above . The amount of peptide or peptide derivative administered to the individual will depend on the type and severity of the disease and on the characteristics of the individual, such as general health, age, sex, body weight and tolerance to drugs. The skilled artisan will be able to determine appropriate dosages depending on these and other factors. Typically, a therapeutically effective amount of the peptide or peptide derivative can range from about 1 mg per day to about 1000 mg per day for an adult. Preferably, the dosage ranges from about 1 mg per day to about 100 mg per day. Parenteral administration can include, for example, systemic administration, such as by intramuscular, intravenous, subcutaneous, or intraperitoneal injection. Peptides or peptide derivatives which resist proteolysis can be administered orally, for example, in capsules, suppositories, suspensions or tablets. The peptide or peptide derivative can be administered to the individual in conjunction with an acceptable pharmaceutical carrier as part of a pharmaceutical composition for treating cancer, arteriosclerosis, osteoporosis or the other diseases discussed above. Suitable pharmaceutical carriers may contain inert ingredients which do not interact with the peptide or peptide derivative. Standard pharmaceutical formulation techniques may be employed such as those described in Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, PA. Suitable pharmaceutical carriers for parenteral administration include, for example, sterile water, physiological saline, bacteriostatic saline (saline containing about 0.9% mg/ml benzyl alcohol), phosphate-buffered saline, Hank's solution, Ringer ' s-lactate and the like. Methods for encapsulating compositions (such as in a coating of hard gelatin or cyclodextran) are known in the art (Baker, et al . , Controlled Release of Biological Active Agents, John Wiley and Sons, 1986) . The HJ loop peptides of the present invention are derived from an array which is linear in the native protein. Therefore, they can be useful in the preparation of specific antibodies against PTKs. Moreover, since the HJ loop sequence is unique to each sub-family of PTK, anti-HJ loop antibodies can be specifically used to isolate distinct sub-families of PTK. Suitable antibodies against an HJ loop peptide can be prepared by conjugating to a suitable carrier, such as keyhole limpet hemocyanin or serum albumin; polyclonal and monoclonal antibody production can be performed using any suitable technique. A variety of methods have been described (see e.g., Kohler et al . , Nature, 256 : 495-497 (1975) and Eur. J. Immunol . 6 : 511- 519 (1976); Milstein et al . , Nature 266 : 550 -552 (1977) ; Koprowski et al . , U.S. Patent No. 4,172,124; Harlow, E. and D. Lane, 1988, An ijod es: A Laboratory Manual , (Cold Spring Harbor Laboratory: Cold Spring Harbor, NY) • Current Protocols In Molecular Biology, Vol. 2 (Supplement 27, Summer 1994), Ausubel, F.M. et al . , Eds., (John Wiley & Sons: New York, NY), Chapter 11, (1991) ) . Generally, a hybridoma can be produced by fusing a suitable immortal cell line (e.g., a myeloma cell line such as SP2/0) with antibody producing cells. The antibody producing cell, preferably those of the spleen or lymph nodes, can be obtained from animals immunized with the antigen of interest. The fused cells (hybridomas) can be isolated using selective culture conditions, and cloned by limiting dilution. Cells which produce antibodies with the desired specificity can be selected by a suitable assay (e.g., ELISA) . Antibodies, including monoclonal antibodies, against HJ loop peptides have a variety of uses. For example, those against or reactive with the protein from which the HJ peptides was derived, and preferably which bind specifically to said protein, can be used to identify and/or sort cells exhibiting that protein on the cell surface (e.g., by flourescence activated cell sorting or histological analyses) . Monoclonal antibodies specific for the protein can also be used to detect and/or quantitate the protein expressed. on the surface of a cell or present in a sample (e.g., in an ELISA) . Alternatively, the antibodies can be used to determine if an intracellular PTK is present in the cytoplasm of the cell. A cleared lysate of the cell is generated (for example, by treating the cells with sodium hydroxide (0.2 N) and sodium dodecyl sulfate (1%) , centrifugating and separating the supernatant from the pellet) followed by treatment with anti-HJ loop antibody specific for the PTK. The cleared lysate is then analzyed, for example, by Western blotting or immunoprecipitation for complexes between PTK and antibody. Some PTKs become membrane-bound or cytoskeleton-associated following stimulation. Anti-HJ loop antibodies can be also utilized for the study of the intracellular distribution (compartmentalization) of various subfamilies of PTKs under various physiologigal conditions via the application of conventional immunocytochemistry such as immunofluoresence, immunoperoxidase technique and immunoelectron microscopy, in conjunction with the specific anti-HJ loop antibodies. Antibodies reactive with the immunogen are also useful. For example, they can be used to detect and/or quantitate immunogen in a sample, or to purify immunogen (e.g., by immunoaffinity purification) . The HJ loop within PTKs plays a key role in regulating the activity of PTKs, as is evidenced by the fact that the peptides and peptide deriviatives of the present invention have such a dramatic effect on the activity of PTKs. The HJ loop peptides of the present invention can also be used to identify ligands which interact with the HJ loops of specific PTKs . For example, an affinity column can be prepared to which a specific HJ loop peptide is covalently attached, directly or via a linker. This column, in turn, can then be utilized for the isolation and identification of specific ligands which bind the HJ loop peptide and which will also likely bind the PTK from which the HJ loop peptide was derived. The ligand can then be eluted from the column, characterized and tested for its effect on PTK activity and the cellular functions which the PTK controls . Serine/threonine kinases are another class of protein kinases. They act as intracellular and, in the case of G protein-coupled receptor kinases, membrane bound proteins involved in cellular signal transduction. Binding of ligand to a serine/theonine kinase results in signal transduction to the interior of the cell, initiated by the phosphorylation of serine or threonine residues of intracellular proteins by the kinase. As with PTKs, serine/threonine kinases control cellular functions by means of this phosphorylation mechanism (Hardie, "Cellular Functions of Protein Kinases", in Hardie and Hanks (ed.) The Protein Kinase FactsBook, Academic Press 1995) . Serine/threonine kinases have a high degree of homology with protein tyrosine kinases, including an HJ loop. Consequently, the activity of serine/threonine kinases, and the cellular functions which they control, can be modulated with peptides which are peptide derivatives of their HJ loops, as discussed above for PTKs. Peptides and peptide derivatives of the HJ loop of serine/threonine kinases and methods of use thereof are disclosed in the concurrently filed and copending application entitled "SHORT PEPTIDES WHICH SELECTIVELY MODULATE THE ACTIVITY OF SERINE/THREONINE KINASES" (Attorney Docket No.CMCC-590, filed May 21, 1997) , the teachings of which are incorporated into this application. Peptide sequences in the compounds of the present invention can be synthesized by solid phase peptide synthesis (e.g., BOC or FMOC) method, by solution phase synthesis, or by other suitable techniques including combinations of the foregoing methods. The BOC and FMOC methods, which are established and widely used, are described in Merrifield, J " . Am . Chem . Soc . 88 : 2149 (1963); Meienhofer, Hormonal Proteins and Peptides, CH. Li, Ed., Academic Press, 1983, pp. 48-267; and Barany and Merrifield, in The Peptides, E. Gross and J. Meienhofer, Eds., Academic Press, New York, 1980, pp. 3- 285. Methods of solid phase peptide synthesis are described in Merrifield, R.B., Science, 232 : 341 (1986); Carpino, L.A. and Han, G.Y., J. Org. Chem . , 37 : 3404 (1972); and Gauspohl , H. et al . , Synthesis, 5 : 315 (1992)) . The teachings of these references are incorporated herein by reference. Methods of cyclizing compounds having peptide sequences are described, for example, in Lobl et al . , WO 92/00995, the teachings of which are incorporated herein by reference in their entirety. Cyclized compounds can be prepared by protecting the side chains of the two amino acids to be used in the ring closure with groups that can be selectively removed while all other side- chain protecting groups remain intact. Selective deprotection is best achieved by using orthogonal side- chain protection such as allyl (OAI) (for the carboxyl group in the side chain of glutamic acid or aspartic acid, for example) , allyloxy carbonyl (Aloe) (for the amino nitrogen in the side chain of lysine or ornithine, for example) or acetamidomethyl (Acm) (for the sulfhydryl of cysteine) protecting groups. OAI and Aloe are easily removed by Pd° and Acm is easily removed by iodine treatment . The invention is illustrated by the following examples which are not intended to be limiting in any way . Example 1 - Preparation of HJ Peptides The novel compounds of this invention can be synthesized utilizing a 430A Peptide Synthesizer from Applied Biosystems using F-Moc technology according to manufacturer's protocols. Other suitable methodologies for preparing peptides are known to person skilled in the art. See e.g., Merrifield, R.B., Science, 232 : 341 (1986); Carpino, L.A., Han, G.Y., J. Org. Chem . , 37 : 3404 (1972); Gauspohl , H., et al . , Synthesis, 5 : 315 (1992)) . The teachings of which are incorporated herein by reference. Rink Amide Resin [4 (2 ',4' Dimethoxyphenyl-FMOC amino methyl) phenoxy resin] was used for the synthesis of C-amidated peptides. The alpha-amino group of the amino acid was protected by an FMOC group, which was removed at the beginning of each cycle by a weak base, 20% piperidine in N-methylpyrrolidone (NMP) . After deprotection, the resin was washed with NMP to remove the piperidine. In si tu activation of the amino acid derivative was performed by the FASTMOC Chemistry using HBTU (2 (1-benzotriazolyl-l-yl) -1,1,3,3- tetramethyluronium) dissolved in HOBt (1-hydroxybenzotriazole) and DMF (dimethylformamide) . The amino acid was dissolved in this solution with additional NMP. DIEA (diisopropylethylamine) was added to initiate activation. Alternatively, the activation ethod of DCC (dicyclohexylcarbodiimide) and HOBt was utilized to form an HOBt active ester. Coupling was performed in NMP. Following acetylation of the N-terminus (optional) , TFA (trifluoroacetic acid) cleavage procedure of the peptide from the resin and the side chain protecting groups was applied using 0.75 g crystalline phenol; 0.25 ml EDT (1 , 2-ethandithiol) ; 0.5 ml thioanisole; 0.5 ml D.I. H 2 0; 10 ml TFA. Example 2 - HJ Peptides Affect the Proliferation of Bovine Capillary Endothelial Cells In Vi tro 96 well, flat bottom, tissue culture microtiter plates were precoated with gelatin (Difco) immediately prior to cell plating by adding 0.100 ml/well of freshly filtered 1% gelatin in glass double distilled water (DDW) . The wells were incubated for about 1 hour at 37°C, and then the excess solution was removed by aspiration. Culture medium was prepared from DMEM, penicillin (100 U/ml) , streptomycin (100 μg/ml) , glutamine (2 mM) , 10% endotoxin free bovine calf serum (Hyclone) and 1 ng/ml of basic fibroblast growth factor (any commericial source) . A bovine capillary endothelial cell (BCE) suspension at 25 x 10 3 cells/ml was prepared in the above described culture medium and distributed 0.160 ml/well (about 4000 endothelial cells/well) . BCE cells are obtained by procedures disclosed in Folkman et al . Proc . Natl . Acad . Sci . USA 76 : 5211 (1979) . A series of HJ peptide stock solutions was prepared by diluting a 10 mM solution of the HJ peptide in 100% DMSO with phosphate buffered saline (PBS) containing 0.1% BSA. The concentration of HJ peptide in each stock solution was adjusted to nine times the desired concentration of the HJ peptide in the assay mixture. 0.020 ml of each HJ peptide stock solution was added to the corresponding wells about 2 hours after BCE plating, with six replicates for each concentration. In addition, BSA solution with no added HJ peptide was used as a control. The wells were incubated for 72-80 hours at 37°C in a 10% C0 2 humidified incubator. The plates were labeled and the medium discarded. Each plate was then washed one time with PBS (0.200 ml/well) . The wells were then fixed by washing with 100% ethanol (0.200 ml/well for 5 minutes). The ethanol was removed and the wells dried completely. Alternatively, the wells were fixed with 4% formaldehyde PBS (PBS buffered 10% formalin from Fisher Scientific- Catalog No. HC200-1) (0.12 ml/well) for at least 30 minutes. Fixing with formaldehyde enhances the O.D. compared with ethanol . The wells were washed one time with borate buffer (0.1 M, pH 8.5). Freshly filtered 1% methylene blue solution (0.600 ml/well) was then added to the wells and incubated for 10 minutes at room temperature. The wells were then washed five times with tap water, after which the wells were dried completely. 0.200 ml/well of 0.1 N HCI (0.1 N) was added to extract the color. After extracting overnight, the O.D. was read at 630 nm to determine the number of cells per well. The procedure for counting cells is described in greater detail in Oliver et al . , J " . of Cell Sci . , 92 : 513 (1989), the teachings of which are incorporated herein by reference. The results for a number of different HJ peptides are shown in Table 1. Also shown in Table 1 are the sequences of each HJ peptide tested and the subsequence of the HJ loop from which each HJ peptide is derived (subsequences of the HJ loop of Src (SEQ ID NO.: 3), Endos (SEQ ID NO.: 47) and NGF-R (SEQ ID NO.: 48)). HJ4 (SEQ ID NO.: 13), HJ12 (SEQ ID NO.: 25) and HJ13 (SEQ ID NO. : 26) are each peptide derivatives of the same subsequence of the HJ loop of Src . HJ4 inhibited BCE cell proliferation; HJ12 and HJ13 stimulated BCE cell proliferation. This result shows that a cellular activity under control of a PTK can be either stimulated or inhibited, depending on the sequence of the peptide derivative used. HJ11 (SEQ ID NO.: 22) also inhibited BCE cell proliferation. HJ11 is a subsequence of a different section of the src HJ loop than HJ4 , HJ11 and HJ13. This result shows that peptide derivatives of different sections of an HJ loop can be used to stimulate or inhibit cellular activities. HJ7 (SEQ ID NO. : 17) is a peptide derivative of the HJ loop of Endos . This HJ peptide also inhibits the proliferation of BCE cells. This result shows that a cellular activity may be controlled by a number of different PTKs and that it is possible to affect the cellular activity by a peptide derivative of the HJ loop of one of the PTKs that control the cellular activity. TABLE 1 SUMMARY OF BCE RESPONSE TO HJ PEPTIDES z3RΩ E- -V-T-K-G-R-V-P-Y-P-G Effect μM HJ4 L-V-T-K-G-R-V Inhibition 40 HJ12 L-V-T-i*-G-R-V S. stimulation 10 HJ13 L-V-T-H-G-R-V S. stimulation 5 HJ11 G-R-V-P-F-P-G Inhibition 5 HJ6 E-L-V-T-K-G-R-V-P-Y No response up to 10 HJ8 L-V-T-K-G-R-V-P-F-P-G No response up to 10 - 3 ( T T Endos E- T - F- S-L-G-G- S- P-Y-P-G Effect HJ7 I- -F-S-L-G-G-S S. stimulation 5 HJ15 G-G-S-P-Y-P-G No response up to 10 HJ9 I- -F-S-L-G-G-S-P-F-P-G No response up to 10 NGF-R F,-T- -F-T-Y-G-K-O-P- -Y-O HJ10 I- -F-T-Y-G-K-Q No response up to 10 HJ14 G-K-Q-P-W-Y-Q No response up to 10 *K = D-Lys; all peptides are N-Acetylated and C-Amidated Example 3 - HJ Peptides Derivatives of c-Src Protect PC-12 Cells From the Effects of Serum Deprivation PC-12 cells were assayed for cell proliferation in the presence of HJ4 and HJ8 according to the procedure described in Example 2 except that 1) the culture medium contained either 2% or 4% horse serum; 2) fibroblast growth factor was not added; and 3) the cells were incubated for eleven days. The cells were counted according to the method described in Example 2. Specifically, the cells were fixed and stained with methylene blue, after which the amount of bound methylene blue was determined. The amount of bound methylene blue measured by the absorbance at 600 nM corresponds to the number of cells present in the wells. The results are shown in Table 2 : TABLE 2 O.D. AT 600 NM (corresponds to the relative cell number) As can be seen, HJ4 and HJ8 both enhance neuronal cell survival . Example 4 - HJ Peptide Derivatives of Protein Tyrosine Kinases Modulate Proliferation of Endothelial Cells In Vi tro Bovine endothelial aortic cells (referred to herein as "A19 cells") were obtained by procedures disclosed in Gospodorowicz et al. Proc . Na tl . Acad . Sci . USA 73 : 4120 (1976) . Mouse MSI and SVR cells were obtained by the procedures disclosed in Arbiser et al . , Proc . Natl . Acad . Sci . 94 : 861 (1997), the teachings of which are incorporated herein by reference. The effect of HJ peptides on cell proliferation was assayed according to the procedure described in Example 2 except that fibroblast growth factor was not added. The cells were counted according to the method described in Example 2. Specifically, the cells were fixed and stained with methylene blue, after which the amount of bound methylene blue was determined. The amount of bound methylene blue measured by the absorbance at 600 nM corresponds to the number of cells present in the wells. The results are shown in Table 3. Table 3 Peptide S.I.* (μM) S.I.* (μM) S.I.* (μM) for SVR Cells for MSI Cells for A19 Cells c-Src HJ4.2 40 HJ4-Nitro 10 HJ11.1 10 HJ20 40 HJ20.1 10 HJ21.1 10 HJ22 40 HJ30 40 Lyn/Hck HJ24 Inactive HJ32 40 c-Abl HJ25 Inactive HJ33 40 40 Csk HJ27 10 HJ31 10 C-Met HJ28 40 FAK HJ34 40 Concentration at which significant inhibition of cell proliferation was observed. HJ peptide derivatives of c-Src, Lyn/Hck, c-Abl, Csk, c-Met and FAK were effective at inhibiting endothelial cell proliferation at concentrations as low as 10 μM. -39 - Example 5 - HJ Peptide Derivatives of Lyn/Hck Cause Changes in the Shape of Vascular Smooth Muscle Cells Bovine vascular smooth muscle cells (VSMC) , obtained by procedures disclosed in Castellot et al . , J. Cell Biol . 102 : 1919 (1986), were grown in culture and incubated with the HJ peptides HJ24 or HJ32, as described in Example 4. After 48 hours, these peptide derivatives demonstrated an outstanding ability to induce a change in the cell shape of the VSMC cells. The cells became elongated and assumed a spindle-like structure. HJ32 was active at 10 and 40 μM and HJ24 was active at 40 μM in causing these morphological changes. Example 6 - K105H101 (SEQ ID NO.: 53), An HJ Peptide Derivatives of DDR2 , Inhibits Proliferation of Endothelial Cells In Vi tro The inhibition of bovine endothelial aortic cells (referred to herein as "A19 cells") by K105H101 (SEQ ID NO.: 53) was tested according to procedures disclosed in Example 4. The results are shown in Figure 4. As can be seen, K105H101 inhibits the proliferation of A19 cells relative to control cells at concentrations greater than about 2.0 μM. Example 7 - K055H101 (SEQ ID NO.: 72), An HJ Peptide Derivatives of Lyn, Inhibits Proliferation of Prostate Cancer Cells In Vi tro The ability of K055H101 to inhibit the proliferation of the cells from the prostate cancer cell line PC3 and DU145 was performed as described in Example 4, except that the tested cells were the human prostate cancer cell lines PC3 and DU145 and that the DU145 cells were grown in RPMI 1640 medium. Both lines were obtained from the American Type Culture Collection (ATCC No. 1435-CRL and 81-HTB) . Also, the plates were not precoated with gelatin. The results are shown in Figures 5 and 6. As can be seen, K055H101 inhibited the proliferation of the DU145 cells relative to control at concentrations greater than about 0.3 μM and the PC3 cell line at concentrations greater than 0.16 μM. Equivalents Those skilled in the art will be able to recognize, or be able to ascertain, using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

Claims: CLAIMS What is claimed is: 1. A peptide comprising a peptide derivative of the HJ loop of a protein tyrosine kinase, wherein: a) said peptide has between about five and about twenty amino acids or amino acid analogs; and b) said peptide modulates activity of the protein tyrosine kinase. 2. The peptide of Claim 1 wherein the peptide is cyclic. 3. The peptide of Claim 1 wherein the peptide is linear. 4. The peptide of Claim 3 wherein the N-terminus and the C-terminus of the peptide is unsubstituted. 5. The peptide of Claim 3 wherein at least one of the the N-terminus or the C-terminus is substituted. 6. The peptide of Claim 5 wherein the N-terminus is amidated and the C-terminus is acylated. 7. The peptide of Claim 1, wherein the peptide derivative has an amino acid sequence corresponding to any subsequence of the amino acid sequence of said HJ loop of said protein tyrosine kinase, with the proviso that any one amino acid in the sequence of the peptide derivative can vary, being any amino acid or analog thereof. 8. The peptide of Claim 7, wherein the protein tyrosine kinase is member of a protein tyrosine kinase family selected from the group consisting of Src, EGF-R, FGF-R, VEGF-R, HGF-R, PDGF-R, insulin receptor family and neurotrophin receptor family. 9. The peptide of Claim 8, wherein the protein tyrosine kinase is from the src family of protein tyrosine kinases and is selected from the group consisting of c-Src, c-Yes, FYN, FGR, HCK, LYN, LCK and BLK. 10. The peptide of Claim 7, wherein the protein tyrosine kinase is selected from group of protein tyrosine kinases consisting of RET, CSK, c-Met, c- Abl and FAK. 11. The peptide of Claim 6, wherein the peptide is a heptapeptide . 12. The peptide of Claim 11, wherein the peptide comprises Leu-Val-Thr-Xaa-Gly-Arg-Val (SEQ ID NO.: 45) , wherein Xaa is selected from the group consisting of L-lysine, D-lysine, histidine, tyrosine, phenylalanine and arginine. 13. The peptide of Claim 11 wherein the peptide comprises Gly-Arg-Val-Pro-Yaa-Pro-Zaa (SEQ ID NO.: 46) , wherein: a) Yaa is selected from the group consisting of tyrosine, phenylalanine and tryptophane; and b) Zaa is selected from the group consisting of glycine, alanine and arginine. -43 - 14. The peptide of Claim 8, wherein the protein tyrosine kinase is from the EGF-R family of protein tyrosine kinases and is selected from the group consisting of EGFR, ErbB2 , ErbB3 and ErB4. 15. The peptide of Claim 8, wherein the protein tyrosine kinase is from the FGF-R family of protein tyrosine kinases and is selected from the group consisting of FGFR1, FGFR2 , FGFR3 and FGFR4. 16. The peptide of Claim 8, wherein the protein tyrosine kinase is from the VEGF-R family of protein tyrosine kinases and is selected from the group consisting of Fltl, Flt4 and Flkl . 17. The peptide of Claim 8, wherein the protein tyrosine kinase is from the insulin receptor family of protein tyrosine kinases and is selected from the group consisting of INS-R, IRR and IGF1-R. 18. The peptide of Claim 8, wherein the protein tyrosine kinase is from the neurotrophin receptor family of protein tyrosine kinases and is selected from the group TrkA, TrkB and TrkC. 19. The peptide of Claim 1, wherein the peptide derivative has an amino acid sequence corresponding to any subsequence of the amino acid sequence of said HJ loop. 20. The peptide of Claim 6, wherein the peptide has the sequence of peptides HJ4 (SEQ ID NO.: 13), HJ4.2 (SEQ ID NO.: 14), HJ4Nitro (SEQ ID NO.: 15), HJ6 (SEQ ID NO.: 16), HJ7 (SEQ ID NO.: 17), HJ7.1 (SEQ ID NO.: 18), HJ8 (SEQ ID NO.: 19), HJ9 (SEQ ID NO.: 20), HJ10 (SEQ ID NO.: 21), HJ11 (SEQ ID NO.: 22), HJ11.1 (SEQ ID NO.: 23), HJllMet (SEQ ID NO.: 24), HJ12 (SEQ ID NO.: 25), HJ13 (SEQ ID NO.: 26), HJ14 (SEQ ID NO.: 27), HJ15 (SEQ ID NO.: 28), HJ18 (SEQ ID NO. : 29), HJ20, (SEQ ID NO.: 30), HJ20.1 (SEQ ID NO.: 31), HJ21.1 (SEQ ID NO.: 32), HJ22 (SEQ ID NO.: 33), HJ23.1 (SEQ ID NO . : 34), HJ24 (SEQ ID NO.: 1), HJ25 (SEQ ID NO.: 35), HJ27 (SEQ ID NO.: 36), HJ28 (SEQ ID NO.: 37), HJ30 (SEQ ID NO.: 38), HJ31 (SEQ ID NO.: 39), HJ32 (SEQ ID NO.: 2), HJ33 (SEQ ID NO. 40), HJ34 (SEQ ID NO.: 41), Lena 1 (SEQ ID NO. 42), Lena 2 (SEQ ID NO.: 43) and J29 (SEQ ID NO. 44) . 21. A peptide having the sequence of peptides HJ4 (SEQ ID NO.: 13), HJ4.2 (SEQ ID NO.: 14), HJ4Nitro (SEQ ID NO.: 15), HJ6 (SEQ ID NO.: 16), HJ7 (SEQ ID NO.: 17), HJ7.1 (SEQ ID NO.: 18), HJ8 (SEQ ID NO.: 19), HJ9 (SEQ ID NO.: 20), HJ10 (SEQ ID NO.: 21), HJ11 (SEQ ID NO.: 22_) , HJ11.1 (SEQ ID NO.: 23_) , HJllMet (SEQ ID NO.: 24), HJ12 (SEQ ID NO.: 25), HJ13 (SEQ ID NO.: 26), HJ14 (SEQ ID NO.: 27), HJ15 (SEQ ID NO.: 28), HJ18 (SEQ ID NO.: 29), HJ20, (SEQ ID NO.: 30), HJ20.1 (SEQ ID NO.: 31), HJ21.1 (SEQ ID NO.: 32), HJ22 (SEQ ID NO.: 33), HJ23.1 (SEQ ID NO.: 34), HJ24 (SEQ ID NO.: 1), HJ25 (SEQ ID NO.: 35), HJ27 (SEQ ID NO.: 36), HJ28 (SEQ ID NO.: 37), HJ30 (SEQ ID NO.: 38), HJ31 (SEQ ID NO.: 39), HJ32 (SEQ ID NO.: 2), HJ33 (SEQ ID NO.: 40), HJ34 (SEQ ID NO.: 41), Lena 1 (SEQ ID NO.: 42), Lena 2 (SEQ ID NO.: 43) and J29 (SEQ ID NO.: 44), with the proviso that any one amino acid residue in the peptide can vary, being any naturally occurring amino acid or analog thereof. 22. A peptide comprising a sequence of amino acids AA. through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: A- L is threonine, or tryptophan; AA 2 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 3 is selected from the group consisting of leucine, isoleucine, methionine and valine; AA 4 is selected from the group consisting of methionine, threonine, serine, valine, isoleucine and leucine; AA 5 is threonine or serine; AA 6 is selected from the group consisting of ornithine, lysine, histidine, tyrosine, arginine, N-nitroarginine, β-cycloarginine, γ~ hydroxyarginine, N-amidinocitruline and 2-amino-4- guanidinobutanoic acid; AA 7 is glycine or alanine; AAg is selected from the group consisting of arginine, N-nitroarginine, β-cycloarginine, γ- hydroxyarginine, N-amidinocitruline, 2-amino-4- guanidinobutanoic acid and lysine; AA 9 is selected from the group consisting of valine, isoleucine, leucine and methionine; AA 10 is proline; AA 1:L is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is proline ; AA 13 is glycine or alanine; AA 14 is selected from the group consisting of methionine, arginine, N-nitroarginine, β- cycloarginine, γ-hydroxyarginine, N- amidinocitruline and 2-amino-4-guanidinobutanoic acid; AA 1S is selected from the group consisting of valine, asparagine, threonine and serine; AA 16 is asparagine or lysine; -46 - AA 17 is selected from the group consisting of arginine, N-nitroarginine, β-cycloarginine, γ~ hydroxyarginine, N-amidinocitruline, 2-amino-4- guanidinobutanoic acid, alanine, and proline; AA 18 is selected from the group consisting of glutamine, asparagine, glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or asparatic acid; AA 19 is selected from the group consisting of valine, isoleucine, leucine and methionine; and AA 20 is selected from the group consisting of leucine, isoleucine, methionine and valine. 23. The peptide of Claim 22, wherein the sequence AA-. through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of c-SRC or Lck, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA X through AA 20 or the subsequence thereof can vary. 24. The peptide of Claim 22, wherein the sequence ΑA 1 through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of c-SRC, with the proviso that any one amino acid in the sequence AA- through AA 20 or the subsequence thereof can vary. 25. The peptide of Claim 23 or Claim 24, wherein the peptide comprises an eight amino acid subsequence of the sequence AA.. through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA 1X through AA 18 . -47 - 26. A peptide comprising a sequence of amino acids AA. through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA- L is tryptophan; AA 2 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 3 is selected from the group consisting of valine, leucine, isoleucine and methionine; AA 4 is selected from the group consisting tyrosine, phenylalanine and tryptophan; AA S is threonine or serine; AA 6 is tyrosine, phenylalanine and tryptophan; AA 7 is glycine or alanine; AA 8 is selected from the group consisting of arginine, N-nitroarginine, β-cycloarginine, y- hydroxyarginine , N-amidinocitruline, 2-amino-4- guanidinobutanoic acid, ornithine, and lysine; AAg is valine or alanine; AA 10 is proline; AA U is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is proline; AA 13 is selected from the group consisting of ornithine, arginine, N-nitroarginine, β- cycloarginine, γ-hydroxyarginine, N- amidinocitruline and 2 -amino-4 -guanidinobutanoic acid and lysine; AA 14 is selected from the group consisting of valine, methionine, isoleucine and leucine; AA 15 is selected from the group consisting of proline, threonine and serine; AA 1S is selected from the group consisting of leucine, isoleucine, valine and methionine; -48 - AA 17 is selected from the group consisting of ornithine, lysine, arginine, N-nitroarginine, β- cycloarginine, γ~hydroxyarginine, N- amidinocitruline and 2 -amino-4 -guanidinobutanoic acid; AA 18 is selected from the group consisting of asparagine, glutamine, glutamic acid, aspartic acid, an aliphatic, substituted aliphatic, benzyl, substituted benzyl or substituted aromatic ester of aspartic acid or glutamic acid; AA 19 is selected from the group consisting of valine, isoleucine, leucine and methionine; and AA 20 is selected from the group consisting of leucine, isoleucine, methionine and valine. 27. The peptide of Claim 26, wherein the sequence AA- through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of Csk, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA X through AA 20 or the subsequence thereof can vary. 28. The peptide of Claim 26, wherein the sequence AA- through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of Csk, with the proviso that any one amino acid in the sequence AA X through AA 20 or the subsequence thereof can vary. 29. The peptide of Claim 27 or Claim 28, wherein the peptide comprises an eight amino acid subsequence of the sequence AA X through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA 1X through AA 18 . 30. A peptide comprising a sequence of amino acids AA X through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA- is tryptophan; AA 2 is glutamic acid or an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or aromatic ester of glutamic acid; AA 3 is selected from the group consisting of isoleucine, leucine, alanine and methionine; AA 4 is selected from the group consisting of alanine, glycine and valine; AA 5 is threonine or serine; AA 6 is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 7 is glycine or alanine; AA 8 is selected from the group consisting of methionine, valine, leucine and isoleucine; AA 9 is serine or threonine; AA 10 is proline; AA X1 is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is proline; AA 13 is glycine or alanine; AA 14 is selected from the group consisting of methionine, isoleucine, valine and leucine; AA 15 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 16 is selected from the group consisting of leucine, isoleucine, proline, lysine, ornithine, arginine, N-nitroarginine, β-cycloarginine, γ~ hydroxyarginine , N-amidinocitruline and 2-amino-4- guanidinobutanoic acid; AA 17 is serine or threonine; - 50 - AA 18 is selected from the group consisting of glutamine, asparagine, glutamic acid, aspartic acid, and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 19 is selected from the group consisting of valine, isoleucine, leucine and methionine; and AA 20 is selected from the group consisting of tyrosine, phenylalanine and tryptophan. 31. The peptide of Claim 30, wherein the sequence AA X through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of c-Abl, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA X through AA 20 or the subsequence thereof can vary. 32. The peptide of Claim 30, wherein the sequence AA X through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of c-Abl, with the proviso that any one amino acid in the sequence AA. through AA 20 or the subsequence thereof can vary. 33. The peptide of Claim 31 or Claim 32, wherein the peptide comprises an eight amino acid subsequence of the sequence AA X through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA through AA 18 . 34. A peptide comprising a sequence of amino acids AA. through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA- L is tryptophan; AA 2 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 3 is selected from the group consisting of leucine, isoleucine, valine and methionine; AA 4 is selected from the group consisting of methionine, leucine, isoleucine and valine; AA 5 is threonine or serine; AA 6 is selected from the group consisting of tyrosine, lysine arginine, ornithine, N- nitroarginine, β-cycloarginine, γ-hydroxyarginine, N-amidinocitruline and 2 -amino-4 -guanidinobutanoic acid; AA 7 is glycine or alanine; AA 8 is glycine or alanine; AA 9 is selected from the group consisting of proline, serine and threonine; AA 10 is proline; AA 1X is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is proline; AA 13 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 14 is selected from the group consisting of valine, methionine, isoleucine and leucine; AA 1S is selected from the group consisting of glutamine, asparagine, glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 16 is threonine or proline; AA 17 is selected from the group consisting of phenylalanine, tyrosine and tryptophan; -52 - AA 18 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 19 is selected from the group consisting of valine, isoleucine, leucine and methionine; and AA 20 is selected from the group consisting of threonine, serine and C-agitated derivatives thereof. 35. The peptide of Claim 34, wherein the sequence AA. through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of c-Met, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA. through AA 20 or the subsequence thereof can vary. 36. The peptide of Claim 34, wherein the sequence AA- through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of c-Met, with the proviso that any one amino acid in the sequence ΑA 1 through AA 20 or the subsequence thereof can vary. 37. The peptide of Claim 35 or Claim 36, wherein the peptide comprises an eight amino acid subsequence of the sequence AA X through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA X1 through AA 18 . 38. A peptide comprising a sequence of amino acids AA. through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA j. is tryptophan; AA 2 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 3 is selected from the group consisting of leucine, isoleucine methionine and valine; AA 4 is selected from the group consisting of methionine, leucine, isoleucine and valine; AA 5 is selected from the group consisting of methionine, valine, isoleucine and leucine; AA 6 is selected from the group consisting of histidine, lysine and ornithine; AA 7 is glycine or alanine; AA 8 is selected from the group consisting of valine, alanine and glycine; AA 9 is selected from the group consisting of lysine, ornithine, arginine, N-nitro arginine, β- cycloarginine, γ-hydroxyarginine, N- amidinocitruline and 2-amino- -guanidinobutanoic acid; AA 10 is proline; AA 1:L is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is glutamine and proline; AA 13 is glycine or alanine; AA 14 is selected from the group consisting of valine, isoleucine, leucine and alamine; AA 15 is selected from the group consisting of lysine, ornithine, arginine, N-nitro arginine, β- cycloarginine, γ-hydroxyarginine, N- amidinocitruline and 2 -amino-4 -guanidinobutanoic acid; AA 16 is selected from the group consisting of glutamine, asparagine, glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, • 54 - substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 17 is selected from the group consisting of glutamine, asparagine, glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of aspartic acid and glutamic acid; AA 18 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 19 is selected from the group consisting of valine, isoleucine, leucine and methionine; and AA 20 is selected from the group consisting of valine, isoleucine, leucine, methionine and C- agitated derivatives thereof. 39. The peptide of Claim 38, wherein the sequence AA- through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of FAK, or a subsequence thereof, with the proviso that any two amino acids in the sequence A - L through AA 20 or the subsequence thereof can vary. 40. The peptide of Claim 38, wherein the sequence A . through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of FAK, with the proviso that any one amino acid in the sequence AA. through AA 20 or the subsequence thereof can vary. 41. The peptide of Claim 39 or Claim 40, wherein the peptide comprises an eight amino acid subsequence of the sequence A 1 through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA X1 through AA 18 . 42. A peptide comprising a sequence of amino acids AA α through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA- L is tryptophan or methionine; AA 2 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 3 is selected from the group consisting of leucine, isoleucine, methionine and valine; AA 4 is selected from the group consisting of methionine, valine, isoleucine and leucine; AA 5 is threonine or serine; AA 6 is selected from the group consisting of phenylalanine, tyrosine and tryptophan; AA 7 is glycine or alanine; AA 8 is selected from the group consisting of arginine, N-nitroarginine, β-cycloarginine, γ- hydroxyarginine , N-amidinocitruline, 2-amino-4- guanidinobutanoic acid, lysine and ornithine; AA 9 is selected from the group consisting of valine, isoleucine, leucine and methionine; AA 10 is proline; AA X1 is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is proline; AA 13 is glycine or alanine; AA 14 is selected from the group consisting of methionine, arginine, N-nitroarginine, β- cycloarginine, γ-hydrσxyarginine, N- amidinocitruline and 2 -amino-4 -guanidinobutanoic acid; AA 15 is threonine or serine; AA 16 is asparagine or glutamine; AA 17 is selected from the group consisting of alanine, glycine or proline; AA 18 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or asparatic acid; AA 19 is selected from the group consisting of valine, isoleucine, leucine and methionine; and AA 20 is selected from the group consisting of leucine, isoleucine, methionine and valine. 43. The peptide of Claim 42, wherein the sequence AA-through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of Lyn or Hck, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA X through AA 20 or the subsequence thereof can vary. 44. The peptide of Claim 42, wherein the sequence ΑA X through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of Lyn or Hck, with the proviso that any one amino acid in the sequence AA X through AA 20 or the subsequence thereof can vary. 45. The peptide of Claim 43 or Claim 44, wherein the peptide comprises an eight amino acid subsequence of the sequence AA X through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA X1 through AA.„. 46. A peptide comprising a sequence of amino acids AA- through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA- L is tryptophan; AA 2 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 3 is selected from the group consisting of leucine, isoleucine, methionine and valine; AA 4 is selected from the group consisting of phenylalanine, tyrosine and tryptophan; AA 5 is threonine or serine; AA 6 is selected from the group consisting of leucine, isoleucine, valine and methionine; AA 7 is glycine or alanine; AA 8 is glycine or alanine; AA 9 is serine or threonine; AA 10 is proline; n is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is selected from the group consisting of proline, cysteine, serine and alanine; AAi 3 is glycine or alanine; AA 14 is selected from the group consisting of methionine, valine, isoleucine and leucine; AA 15 is selected from the group consisting of serine, threonine, methionine, proline, lysine, ornithine, glutamine and asparagine; AA 16 is selected from the group consisting of cysteine, serine, methionine, valine, isoleucine and leucine; AA 17 is selected from the group consisting of alanine, asparagine, aspartic acid, and an aliphatic or substituted aliphatic ester of aspartic acid, benzyl, substituted benzyl, aromatic or substituted aromatic ester of asparatic acid; AA 18 is selected from the group consisting of threonine, serine, glutamic acid, aspartic, acid and an aliphatic substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid; AA 19 is selected from the group consisting of threonine, leucine, glutamine, asparagine, glutamic acid, aspartic acid and an aliphatic substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; and AA 20 is selected from the group consisting of tyrosine, phenylalanine and tryptophan. 47. The peptide of Claim 46, wherein the sequence AA. through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of Endoth, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA X through AA 20 or the subsequence thereof can vary. 48. The peptide of Claim 46, wherein the sequence AA X through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of Endoth, with the proviso that any one amino acid in the sequence AA- through AA 20 or the subsequence thereof can vary. 49. The peptide of Claim 47 or Claim 48, wherein the peptide comprises an eight amino acid subsequence of the sequence AA- through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA X1 through AA 18 . 50. A peptide comprising a sequence of amino acids AA X through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA 1 is tryptophan; AA 2 is selected from the group consisting of glutamic acid, aspartic acid and an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 3 is selected from the group consisting of leucine, isoleucine, methionine and valine; AA 4 is selected from the group consisting of phenylalanine, tyrosine and tryptophan; AA S is threonine or serine; AA 6 is selected from the group consisting of phenylalanine, tyrosine and tryptophan; AA 7 is glycine or alanine; AA 8 is lsyine or ornithine; AA 9 is glutamine or asparagine; AA 10 is proline ; AA X1 is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 12 is selected from the group consisting of tyrosine, phenylalanine and tryptophan; AA 13 is glutamine or asparagine; AA 14 is selected from the group consisting of leucine, isoleucine, methionine and valine; AA 15 is serine or threonine; AA 16 is glutamine or asparagine; AA 17 is threonine or asparagine; AA 18 is selected from the group consisting of glutamic acid, asparatic acid, and a substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 19 is selected from the group consisting of glycine, alanine and valine; and AA 20 is selected from the group consisting of leucine, isoleucine, methionine and valine. 51. The peptide of Claim 50, wherein the sequence AA- through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of Trk-NGFR, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA.. through AA 20 or the subsequence thereof can vary. 52. The peptide of Claim 50, wherein the sequence AA X through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of Trk-NGFR, with the proviso that any one amino acid in the sequence AA. through AA 20 or the subsequence thereof can vary. 53. The peptide of Claim 51 or Claim 52, wherein the peptide comprises an eight amino acid subsequence of the sequence AA.. through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA X1 through AA 18 . 54. A peptide comprising a sequence of amino acids AA X through AA 20 or a subsequence thereof comprising at least five amino acids, wherein: AA-. is glutamic acid, aspartic acid or an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 2 leucine, isoleucine, methionine or valine; AA 3 serine, threonine or proline; AA 4 is phenylalanine, tyrosine or tryptophan; AA 5 is glutamic acid, aspartic acid or an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 6 is leucine, isoleucine, methionine or valine; AA 7 is leucine, isoleucine, methionine or valine; AA 8 is threonine or serine; AA 9 is phenylalanine, tyrosine or tryptophan; AA 10 is glycine or alanine; AA 1X is serine, alanine, threonine or glycine; AA 12 is lysine, ornithine, arginine, N- nitroarginine, β-cycloarginine, γ-hydroxyarginine, N-amidinocitruline or 2 -amino-4 -guanidinobutanoic acid; AA 13 is proline; AA 14 is tyrosine, phenylalanine or tryptophan; AA 15 is glutamic acid, aspartic acid or an aliphatic, substituted aliphatic, benzyl, substituted benzyl, aromatic or substituted aromatic ester of glutamic acid or aspartic acid; AA 16 is glycine or alanine; AA 17 is leucine, isoleucine, methionine or valine; AA 18 is proline; AA 19 i s glycine, alanine, serine or threonine; and AA 20 is serine, arginine, N-nitroarginine, β- cycloarginine, γ-hydroxyarginine, N- amidinocitruline or 2-amino-4-guanidinobutanoic acid. 55. The peptide of Claim 54, wherein the sequence AA. through AA 20 or the subsequence thereof corresponds to the sequence of the HJ loop of EGFR, or a subsequence thereof, with the proviso that any two amino acids in the sequence AA X through AA 20 or the subsequence thereof can vary. 56. The peptide of Claim 54, wherein the sequence AA X through AA 20 or the subsequence thereof corresponds to the sequence or a subsequence of the HJ loop of EGFR, with the proviso that any one amino acid in the sequence AA 2 through AA 20 or the subsequence thereof can vary. 57. The peptide of Claim 55 or Claim 56, wherein the peptide comprises an eight amino acid subsequence of the sequence AA 2 through AA 20 , wherein the subsequence is selected from the group consisting of AA 3 through AA 10 , AA 7 through AA 14 and AA-- through AA 18 . 58. A method of identifying a peptide which modulates the activity of a protein tyrosine kinase comprising the steps of: a) providing a peptide, referred to as a "test peptide", comprising a peptide derivative of the HJ loop of said protein tyrosine kinase and having from about five to about twenty amino acids or analogs thereof; b) incubating the test peptide with cells having one or more cellular activities controlled by a protein tyrosine kinase under conditions suitable for assessing activity of the protein tyrosine kinase; c) assessing activity of the protein tyrosine kinase, wherein greater or lesser activity compared with the cells grown without incubation of the test peptide indicates that the peptide modulates activity of the protein tyrosine kinase. 59. The method of Claim 58, wherein the activity of the protein tyrosine kinase is assessed by measuring the rate of survival or proliferation of said cells in tissue culture. 60. A peptide which modulates activity of a protein tyrosine kinase, wherein the peptide is identified by the method of Claim 58. 61. A method of modulating activity of a protein tyrosine kinase in a subject, comprising administering a therapeutically effective amount of a peptide comprising a peptide derivative of the HJ loop of the protein tyrosine kinase, wherein: a) said peptide has betn about five and about twenty amino acids or amino acid analogs; and b) said peptide modulates activity of the protein tyrosine kinase; c) the N-terminus of said peptide is unsubstituted or acylated; and d) the C-terminus of said peptide is unsubstituted or amidated.

Inventors: BEN-SASSON SHMUEL A, BEN-SASSON, SHMUEL, A.
Applicants: BEN SASSON SHMUEL A, CHILDRENS MEDICAL CENTER, BEN-SASSON, SHMUEL, A., THE CHILDREN'S MEDICAL CENTER CORPORATION
Application year: 1998
Main classification: C12N9
IPC codes: A61K38, A61P9, A61P17, A61P35, C07K7, C12N9