bluuebunny/crossref_metadata_2025 huggingface dataset:
Allospecific and virus-specific cytolytic T lymphocytes are restricted to the N or C1 domain of H-2 antigens expressed on L cells after DNA-mediated gene transfer.
Authors: Reiss C S , Evans G A , Margulies D H , Seidman J G , Burakoff S J
Published: May 2006

In order to identify the site(s) on major histocompatibility molecules recognized by cytolytic T lymphocytes (CTLs), the recognition of H-2 antigens expressed when cloned genes are introduced into mouse L cells by DNA-mediated gene transfer has come under investigation. Recently, recombinant H-2 genes have been constructed in vitro from restriction endonuclease fragments of cloned H-2Dd and H-2Ld genes which exchange the N and C1 external domains (exon shuffling). These hybrid H-2 genes direct the synthesis of hybrid H-2 antigens when introduced into L cells by DNA-mediated gene transfer. These transformed L cells have been used as target cells to achieve a more precise localization of the sites recognized by allospecific and virus-specific CTLs. CTL systems were chosen that allow one to probe allospecific Ld or Dd recognition or virus-restricted Ld or Dd recognition. Using this approach we were able to map essential CTL recognition sites to the N and C1 domains of class 1 molecules.
Normal mice express idiotypes related to autoantibody idiotypes of lupus mice
Authors: Datta Syamal K. , Stollar B. David , Schwartz Robert S.
Published: May 2006

Spleen and fetal liver B cells of normal mice synthesized idiotypes shared by anti-DNA autoantibodies of genetically autoimmune mice. Some of the idiotypes were specific for DNA; the majority, however, were not. The findings indicate that the autoantibody idiotypes are related to a conserved family of antibody variable regions that are present in normal animals.
Development of large granular lymphocytes with anomalous, nonspecific cytotoxicity in clones derived from Ly-2+ T cells.
Authors: Shortman K , Wilson A , Scollay R , Chen W F
Published: May 2006

T cells cultured at limit dilution for 8 days in a concanavalin A-stimulated, filler-cell and growth factor-supported system produced cytolytic clones with high efficiency. These clones were not specific, lysing a wide range of targets, syngeneic and allogeneic, of tumor and normal cell origin. Lysis was a cell-mediated phenomenon but was not blocked by anti-Ly-2. One H-2-negative target was lysed, but one was resistant. Xenogeneic (human) tumor cells were not lysed. The cells in the clones were large, vacuolated, granular lymphocytes. They originated from single Ly-2+ responder cells and not from irradiated filler cells. Therefore, activated lymphocyte killers and other natural killer-like cells may be differentiated elements of the Ly-2+ T-cell lineage.
Spatial localization of bleaching adaptation in isolated vertebrate rod photoreceptors.
Authors: Cornwall M C , Fein A , MacNichol E F
Published: May 2006

Bleaching of a large fraction of the rhodopsin in isolated rod outer segments results in an irreversible desensitization of the rod. This desensitization is referred to as bleaching adaptation. The logarithm of the sensitivity of the rod during bleaching adaptation has been found by a number of workers to be linearly related to the concentration of unbleached rhodopsin. We have measured the desensitization due to bleaching adaptation produced by a spatially confined stimulus and found that its effects are highly local. The space constant for the spread of desensitization was less than 4 microns. The small apparent spread of desensitization beyond the bleached regions probably can be accounted for by defocusing and light scatter. Thus, the involvement of a freely diffusible transmitter in bleaching adaptation does not appear to be required.
Amphipathic analysis and possible formation of the ion channel in an acetylcholine receptor.
Authors: Finer-Moore J , Stroud R M
Published: May 2006

Fourier analysis of the hydrophobicities of the acetylcholine receptor subunit sequences reveals regions of amphipathic secondary structure. Prediction of a consensus secondary structure based on this analysis and on an empirical prediction method leads to a testable hypothesis about how the ion channel is formed and might function. Knowledge of the three-dimensional structure of acetylcholine receptors is consistent with features of the model proposed and provides some constraints.
Characterization of mouse myelin basic protein messenger RNAs with a myelin basic protein cDNA clone.
Authors: Zeller N K , Hunkeler M J , Campagnoni A T , Sprague J , Lazzarini R A
Published: May 2006

Using a family of synthetic tetradecamer oligonucleotides as a primer for cDNA synthesis and a second family of tetradecamers as a hybridization probe, we have prepared and isolated a cDNA clone of mouse myelin basic protein (MBP). The clone, pNZ111, corresponds to the region of the mRNA that codes for an amino acid sequence present in all four major forms of MBP. The relative abundance of MBP mRNA, estimated by dot blot hybridization, increased with the age of the mouse to a maximum at 18 days, then decreased to about one-fourth of that amount at later ages. Mouse MBP mRNAs, selected by their ability to hybridize to the clone, translate into the four forms of myelin basic protein. In RNA blot analyses, pNZ111 hybridized to multiple species of mouse mRNA. The predominant hybridization is to a broad band of RNAs ranging in length from 2,350 to 2,100 bases. These mRNA species are extremely long, considering that the largest MBP could be encoded by approximately 600 bases. In addition to these, there are also minor bands that hybridize with pNZ111, including a band of 4,100 bases and smaller ones of 1,900, 1,500, and 1,200 bases.
RNase III cleavage is obligate for maturation but not for function of Escherichia coli pre-23S rRNA.
Authors: King T C , Sirdeshmukh R , Schlessinger D
Published: May 2006

RNase III makes the initial cleavages that excise Escherichia coli precursor 16S and 23S rRNA from a single large primary transcript. In mutants deficient in RNase III, no species cleaved by RNase III are detected and the processing of 23S rRNA precursors to form mature 23S rRNA fails entirely. Instead, 50S ribosomes are formed with rRNAs up to several hundred nucleotides longer than mature 23S rRNA. Unexpectedly, these aberrant subunits function well enough to participate in protein synthesis and permit cell growth. Consistent with the inference that RNase III cleavages are absolutely required for 23S rRNA maturation, when 50S ribosomes from a strain deficient in RNase III were incubated with a ribosome-free extract from a RNase III+ strain, rRNA species processed by RNase III and species with normal mature 23S rRNA termini were produced.
A molecular approach to leukemogenesis: mouse lymphomas contain an activated c-ras oncogene.
Authors: Guerrero I , Calzada P , Mayer A , Pellicer A
Published: May 2006

By inducing mouse thymomas with carcinogens and gamma-radiation, we have studied the potential of tumor DNA to induce foci in rodent fibroblasts. A high percentage of the tumors used transformed the cultured cells, and the oncogenic phenotype segregated with extra copies of the c-ras gene family. There appears to be selectivity in the activated gene because so far all analyzed tumors induced by carcinogen have activated the N-ras gene, and those induced by radiation have activated the K-ras gene. The K-ras gene is the cellular counterpart of the viral ras oncogene in Kirsten murine sarcoma virus, but the N-ras has not yet been found in a retrovirus. The transformed cells have a marked increase in expression of the oncogene at the RNA and protein level. This model system might be a powerful tool in the study of leukemogenesis.
Inhibition of malignant transformation in vitro by inhibitors of poly(ADP-ribose) synthesis.
Authors: Borek C , Morgan W F , Ong A , Cleaver J E
Published: May 2006

Malignant transformation in vitro of hamster embryo cells and mouse C3H 10T 1/2 cells by x-rays, ultraviolet light, and chemical carcinogens was inhibited by benzamide and by 3-aminobenzamide at concentrations that are specific for inhibition of poly(ADP-ribose) formation. These compounds slow the ligation stage of repair of x-ray and alkylation damage but not of ultraviolet light damage. At high concentrations they also inhibited de novo synthesis of DNA purines and DNA methylation by S-adenosylmethionine. The suppression of transformation by the benzamides is in striking contrast to their reported effectiveness in enhancing sister chromatid exchange, mutagenesis, and killing in cells exposed to alkylating agents. Our results suggest that mechanisms regulating malignant transformation are different from those regulating DNA repair, sister chromatid exchange, and mutagenesis and may be associated with changes in gene regulation and expression caused by alterations in poly(ADP-ribosyl)ation.
Molecular abnormality of an inactive aldehyde dehydrogenase variant commonly found in Orientals.
Authors: Yoshida A , Huang I Y , Ikawa M
Published: May 2006

Usual human livers contain two major aldehyde dehydrogenase [(ALDH) aldehyde:NAD+ oxidoreductase] isozymes--i.e., a cytosolic ALDH1 component and a mitochondrial ALDH2 component--whereas approximately equal to 50% of Orientals are "atypical" and have only the ALDH1 isozyme and are missing the ALDH2 isozyme. We previously demonstrated that atypical livers contain an enzymatically inactive but immunologically crossreactive material (CRM) corresponding to the ALDH2 component. The enzymatically active ALDH2 obtained from a usual liver and the CRM obtained from an atypical liver were reduced, S-carboxymethylated, and digested by trypsin. Separation of their digests by high-performance reverse-phase chromatography and by two-dimensional paper chromatography and electrophoresis revealed that ALDH2 contained a peptide sequence of -Glu-Leu-Gly-Glu-Ala-Gly-Leu-Gln-Ala-Asn-Val-Gln-Val-Lys- and that the glutamine adjacent to lysine was substituted by lysine in CRM. All other tryptic peptides, including eight peptides containing S-carboxymethylcysteine, were common in ALDH2 and CRM. It is concluded that a point mutation in the human ALDH2 locus produced the glutamine leads to lysine substitution and enzyme inactivation.
Attenuation of the ilvB operon by amino acids reflecting substrates or products of the ilvB gene product.
Authors: Hauser C A , Hatfield G W
Published: May 2006

Transcription termination at the ilvB attenuator of Escherichia coli K-12 has been quantitated by measuring the in vivo rate of synthesis and degradation of mRNA segments proximal and distal to the attenuator. This analysis demonstrates that a 4-fold deattenuation results in vivo when the growth of cells is limited by the availability of valine or leucine. The result suggests that attenuation is the major mechanism by which this operon is regulated by these end-product amino acids. On the basis of possible secondary structures of ilvB leader RNA, we predicted that attenuation of this operon should also be affected by growth of cells in limiting amounts of alanine or threonine. We report here that the ilvB operon is deattenuated when cells are starved for either of these amino acids. A rationale for the regulation of this operon by these four amino acids, which represent both the substrates and the products of the ilvB gene product, and by catabolite repression is presented.
Structure and expression of a pea nuclear gene encoding a chlorophyll a/b-binding polypeptide
Authors: Cashmore Anthony R.
Published: May 2006

A nuclear gene
AB80
has been isolated from a phage λ Charon 4 library of pea DNA. The sequence of the gene has been determined and it has been shown to contain an uninterrupted reading frame of 269 amino acids, corresponding to a precursor to a constituent polypeptide of the light-harvesting chlorophyll a/b-protein complex. Primer extension and S1 nuclease studies defined a cap site for
AB80
. The first methionine codon 3′ from this site is 69 nucleotides away and is the initiating codon of the open reading frame. A “TATA” sequence occurs 31 nucleotides 5′ from the cap site. A second TATA sequence is found 7 nucleotides on the 5′ side of the initiating methionine codon and the sequences surrounding this TATA sequence are strikingly similar to those surrounding the first TATA sequence. The mature polypeptide encoded by
AB80
differs by 5 amino acids from the polypeptide corresponding to a previously characterized cDNA sequence pAB96. This result is indicative of heterogeneity within the constituent polypeptides of the light-harvesting chlorophyll a/b-protein complex. The sequence Arg-Lys-Ser-Ala-Thr-Thr-Lys-Lys occurs at, or near, the NH
2
-terminus of the mature polypeptide encoded by
AB80
. This basic peptide is of interest because of its apparent involvement in changes in excitation-energy distribution in chloroplast membranes. Some general similarities, but no extensive sequence homology, is found on comparing the transit sequence for the precursor to the chlorophyll a/b-binding polypeptide with the transit sequences previously determined for the precursors to the small subunit of ribulose-1,5-bisphosphate carboxylase.
Formation of cyanide from carbon 1 of 1-aminocyclopropane-1-carboxylic acid during its conversion to ethylene
Authors: Peiser Galen D. , Wang Tsu-Tsuen , Hoffman Neil E. , Yang Shang Fa , Liu Hung-wen , Walsh Christopher T.
Published: May 2006

It has been shown that 1-aminocyclopropane-1-carboxylic acid (ACC) is the immediate precursor of ethylene, which is derived from C-2 and C-3 of ACC. When [1-
14
C]ACC was administered to etiolated mungbean (
Vigna radiata
) hypocotyls, ≈16% of the ACC was converted to ethylene and about 10% of the radioactivity was converted to [
14
C]asparagine in 7 hr. In etiolated epicotyls of common vetch (
Vicia sativa
), after 7 hr about 14% of the ACC was converted to ethylene and 16% of the radioactivity was converted to β-cyanoalanine plus γ-glutamyl-β-cyanoalanine. Itis known that in most plants cyanide is metabolized to asparagine via the intermediate β-cyanoalanine, whereas in a fewplants such as
V. sativa
, β-cyanoalanine is converted to the conjugate γ-glutamyl-β-cyanoalanine. We confirmed that [
14
C]cyanide was metabolized into [
14
C]asparagine in mungbean and into [
14
C]cyanoalanine plus its conjugate in
V. sativa
. Moreover, after feeding plant tissue with [1-
14
C]ACC, [
14
C]asparagine isolated from mungbean and β-[
14
C]cyanoalanine from
V. sativa
were labeled in the C-4 position, as would be expected if these two compounds were derived from [
14
C]cyanide. When the conversion of ACC to ethylene in
V. sativa
tissue was inhibited by high temperature (41°C), the conversion of [1-
14
C]ACC to β-[
14
C]cyanoalanine and γ-glutamyl-β-[
14
C]cyanoalanine was similarly inhibited. When [
carboxyl
-
14
C]ACC was administered to mungbean and
V. sativa
,
14
CO
2
was recovered in an amount equivalent to the amount of ethylene produced. These data indicate that in the conversion of ACC to ethylene the carboxyl group yields CO
2
, and C-1 is released as HCN.
Localization of cytochrome P1-450 and P3-450 genes to mouse chromosome 9.
Authors: Tukey R H , Lalley P A , Nebert D W
Published: May 2006

Treatment of mice with polycyclic aromatic hydrocarbons results in the induction of P1-450 and P3-450 forms of cytochrome P-450. The genes for both cytochromes have recently been cloned and shown to be coordinately regulated by the Ah receptor. The mouse analogues of P1-450 and P3-450 can be distinguished from their hamster counterparts by Southern blot analysis with Kpn I-digested DNA fragments. DNA from hamster-mouse somatic cell hybrids that have selectively lost mouse chromosomes was used in Southern blots to map the location of the two mouse genes. Chromosome segregation analysis of 12 hybrid clones demonstrated that the structural genes for both P1-450 and P3-450 can be assigned to mouse chromosome 9.
Idiotypic determinants of natural IgM antibodies that resemble self Ia antigens.
Authors: Holmberg D , Forsgren S , Forni L , Ivars F , Coutinho A
Published: May 2006

A collection of immunoglobulin-secreting B-cell hybridomas was derived from normal neonatal BALB/c spleen and searched for reactivity against a panel of monoclonal anti-H-2 antibodies. We describe here one IgM antibody which was found to react with the monoclonal anti-Ia.7 antibody 14-4-4S. The characterization of this clone (BA.N 4:4.57) revealed its anti-trinitrophenyl specificity and demonstrated specific binding to five different monoclonal anti-Ia.7 antibodies but not to other anti-H-2 antibodies. The variable region specificity of these interactions was shown by the use of pepsin Fab fragments of the IgM antibody. Anti-Ia.7 antibodies were shown to specifically inhibit plaque formation by the hybridoma cells, and dinitrophenylglycine was shown to inhibit the reaction between the IgM antibody and anti-Ia.7 molecules. We interpret these results as to indicate that BA.N 4:4.57 expresses an idiotope or idiotopes which mimic Ia.7 determinants. This idiotypic family is naturally expressed in both newborn and adult BALB/c mice, as shown by the presence in normal serum of IgM molecules that specifically react with the F(ab')2 fragment of the 14-4-4S antibody. We speculate on the importance of idiotypic mimicry with major histocompatibility complex determinants, for both the selection of natural antibody repertoires and the evolution of antibody genes.
Pulse labeling of small nuclear ribonucleoproteins in vivo reveals distinct patterns of antigen recognition by human autoimmune antibodies.
Authors: Fisher D E , Reeves W H , Conner G E , Blobel G , Kunkel H G
Published: May 2006

Antibodies directed against small nuclear ribonucleoprotein ( snRNP ) particles are found in the Sm and RNP autoimmune sera from numerous patients with systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD). These two reactivities differ in disease distribution as well as antigen specificity. Although sera from both of these autoimmune syndromes contain snRNP reactive antibodies, distinction in antigen binding specificity have been difficult to define because of the particulate nature of the snRNP antigen. To overcome this problem, while retaining the antigen in a native state, cells were pulse-labeled with [35S]methionine for 8 min to generate radioactive snRNP proteins in forms reflecting incomplete de novo particle assembly. Immunoprecipitation of snRNP antigen prepared in this manner revealed clearly distinct patterns of Sm and RNP immunorecognition . While Sm sera precipitated all eight labeled snRNP proteins, RNP antibodies precipitated only two of the eight. However, a brief pulse followed by periods of cold chase demonstrated that RNP sera can eventually coprecipitate all components of the complete particle. In addition to antibodies to the other six snRNP peptides, all Sm sera tested have been found to contain the RNP-like reactivity with snRNP proteins A and C. RNP reactivity with these two components is of particular interest because these proteins are unique in the metabolism of snRNPs. Defining and distinguishing the precise peptides recognized by Sm and RNP antibodies has helped to clarify the biochemical basis of the standard laboratory tests for these antigen reactivities.
Detection of non-A, non-B hepatitis antigen by immunocytochemical staining.
Authors: Burk K H , Oefinger P E , Dreesman G R
Published: May 2006

Liver tissue obtained from a chimpanzee during the acute phase of an experimental non-A, non-B (NANB) hepatitis virus infection was studied by a sensitive immunocytochemical staining procedure for the presence of NANB viral antigens. Initial investigations were conducted with a model system of hepatitis B virus (HBV) antigens for purposes of comparing two immunocytochemical staining methods. Of these two procedures, an immunoperoxidase procedure, utilizing an avidin-biotinylated enzyme complex, was at least 40-fold more sensitive than a conventional immunoperoxidase technique for the detection of HBV-specific tissue antigens. Utilization of the avidin-biotin-amplified immunoperoxidase staining procedure, in conjunction with four primary convalescent antisera obtained from NANB hepatitis-implicated donors, resulted in the observation of NANB virus-associated antigen in the cytoplasm of hepatocytes from an infected chimpanzee liver. These same human antisera were not reactive with a number of uninfected control cells nor with cells infected with HBV, hepatitis A virus, or cytomegalovirus. Preincubation of one of these convalescent NANB sera, or IgG derived thereof, with an acute-phase serum obtained from a NANB hepatitis virus-infected chimpanzee abolished the antibody reactivity. We conclude from these observations that selected convalescent sera from NANB hepatitis virus-infected patients contain low levels of antibody that specifically react with a cytoplasmic antigen associated with NANB virus-infected hepatocytes.
Epoxidation of olefins by cytochrome P-450 model compounds: mechanism of oxygen atom transfer.
Authors: Collman J P , Brauman J I , Meunier B , Raybuck S A , Kodadek T
Published: May 2006

The mechanism of the Mn(III) porphyrin-catalyzed epoxidation of olefins by lithium hypochlorite is examined. The active oxidant is thought to be a high-valent manganese-oxo complex. It is shown that a relatively stable intermediate is reversibly formed upon interaction of the olefin and the oxo complex. The decomposition of this intermediate to Mn(III) porphyrin and epoxide is the rate-determining step of the catalytic cycle. Some analogies to the biochemical epoxidation of olefins catalyzed by cytochrome P-450 are discussed.
Structure of the Trg protein: Homologies with and differences from other sensory transducers of Escherichia coli.
Authors: Bollinger J , Park C , Harayama S , Hazelbauer G L
Published: May 2006

Transducer proteins are central to chemotaxis in Escherichia coli. Three transducer genes comprise a homologous gene family, while a fourth gene, trg, is more distantly related. We have determined the nucleotide sequence of trg. The deduced sequence of the Trg protein has features in common with other transducers as well as regions of significant divergence. The protein sequence suggests the same transmembrane structure postulated for other transducers: an extra cytoplasmic NH2-terminal domain connected by a membrane-spanning region to an intracellular COOH-terminal domain. The COOH-terminal domain of Trg exhibits substantial sequence identity with the corresponding domains of the other transducers, particularly near the sites of covalent modification. Trg appears to have the same five methyl-accepting sites identified in the Tsr protein. Two of those sites are glutamines that are deamidated to yield methyl-accepting glutamates, while the remainder are synthesized as glutamates. Conservation in number but not in position of modified glutamines in Trg compared to the other transducers is consistent with the notion that uncharged glutamines at a specific number of modification sites serve to balance the signaling state of newly synthesized transducers. The NH2-terminal domain of Trg exhibits no significant homology with other transducers, implying that trg may be a fusion of the common COOH-terminal transducer sequence with an unrelated NH2-terminal sequence. The location of specific mutations within trg provides support for the suggestion that ligand-binding sites are in the NH2-terminal domains.
Essential sites at transposon Tn 10 termini.
Authors: Way J C , Kleckner N
Published: May 2006

We describe here point and deletion mutations that define which sequences at the termini of Tn10 are essential for transposition. We conclude that at least 13 and no more than 27 base pairs of terminal IS10 sequence are absolutely required at each end. These sequences correspond closely to the terminal inverted repeats of IS10. Sequences between base pairs 27 and 70 at each terminus and certain non-IS10 sequences can also influence transposition, but to a lesser degree. We also describe properties of many function-defective Tn10 transposition mutants and one exceptional Tn10 mutant.
31P NMR study of improvement in oxidative phosphorylation by vitamins K3 and C in a patient with a defect in electron transport at complex III in skeletal muscle.
Authors: Eleff S , Kennaway N G , Buist N R , Darley-Usmar V M , Capaldi R A , Bank W J , Chance B
Published: May 2006

The bioenergetic capacity of skeletal muscle in a 17-year-old patient with a severe defect in complex III of the electron transport chain has been examined by 31P NMR measurements of the molar ratio of phosphocreatine to inorganic phosphate (PCr/Pi). Resting ratios were 1.3-2.5, which can be compared with roughly 8.6 for a young, normal female control at rest. Quantitative evaluation of the activity of oxidative metabolism was afforded by the rate of recovery of PCr/Pi from exercise and was found to be 2.5% of normal. After administration of menadione and ascorbate, we found a 21-fold increase of the recovery rate relative to the pretherapy value, to within 56% of the recovery rate of the young female control. Thus, NMR examinations of skeletal muscle at rest and in recovery from activity document marked improvement to specific drug therapy in the electron transport capabilities and the ATP synthesis rate of a patient with a deficiency in a cytochrome b-containing complex III. Improvements in functional ability, although not as dramatic as biochemical changes, are also apparent.
Identification of a site on 23S ribosomal RNA located at the peptidyl transferase center.
Authors: Barta A , Steiner G , Brosius J , Noller H F , Kuechler E
Published: May 2006

3-(4'-Benzoylphenyl)propionyl[3H] Phe-tRNA bound to the peptidyl site of the ribosome is photo-crosslinked exclusively to 23S RNA on irradiation at 320 nm. The site of reaction has been identified both by hybridization and primer-extension experiments as uridine-2584 and uridine-2585, located within the central loop of domain V according to the secondary structure model of 23S RNA. The fact that the covalently crosslinked tRNA retains its ability to form a peptide bond, together with the proximity of this site to the position of several mutations leading to chloramphenicol or erythromycin resistance strongly argue that this region of the 23S-like rRNAs is an integral component of the peptidyl transferase site. On the basis of these results, and from comparative analysis of the 16 available large subunit rRNA sequences, we propose a model for the functional organization of the peptidyl transferase site involving interaction of domains II and V of 23S rRNA.
Adenovirus tripartite leader sequence enhances translation of mRNAs late after infection.
Authors: Logan J , Shenk T
Published: May 2006

A series of adenovirus type 5 variants was constructed to probe the function of the tripartite leader sequence, a 200-nucleotide, 5' noncoding sequence carried on the majority of late viral mRNAs. Recombinant plasmids were constructed that carried the major late transcriptional control region followed by portions of the tripartite leader sequence fused to the E1A coding region. These modified E1A genes were then rebuilt into intact viral chromosomes, replacing the corresponding wild-type region. The leader segments had no effect on the translation of E1A mRNAs early after infection, but the tripartite leader significantly enhanced (5-fold) the efficiency with which the mRNAs were translated late after infection.
Nucleotide sequence of the Escherichia coli prolipoprotein signal peptidase (lsp) gene.
Authors: Innis M A , Tokunaga M , Williams M E , Loranger J M , Chang S Y , Chang S , Wu H C
Published: May 2006

The nucleotide sequence of the prolipoprotein signal peptidase (lsp) gene has been determined. The lsp gene was found to be adjacent to the isoleucyl-tRNA synthetase ( ileS ) gene, such that the termination codon of the ileS gene overlaps with the initiation codon of lsp. These two genes are transcribed in the same direction and the major promotor for the lsp gene appears to be upstream of ileS . Identification of the lsp gene was established by amplification of prolipoprotein signal peptidase activity in strains carrying a subcloned 1.1-kilobase Stu I-Acc I fragment and was further confirmed by introducing mutational alterations in the COOH terminus of the protein that caused a decrease in prolipoprotein signal peptidase activity. The deduced amino acid sequence indicates that prolipoprotein signal peptidase contains 164 residues. Unlike most exported proteins, there is no apparent signal peptide sequence for the lsp protein. Computer-assisted secondary structure analysis of the deduced amino acid sequence identified four hydrophobic regions that share features common to transmembrane segments in integral membrane proteins.
Application of the Dale-Eisinger analysis to proximity mapping in the contractile system.
Authors: Torgerson P M , Morales M F
Published: May 2006

Fluorescence anisotropy decays were used to quantify the degree of rapid librational motion associated with several fluorescent probes attached to contractile proteins. This information allows an analysis of how far kappa 2, the resonance energy transfer orientation factor, may deviate from the dynamically averaged value of 2/3. Extrema can then be set on R0, the critical transfer distance, and hence on the interprobe distance. These results set maximum ranges on possible distances between several probe pairs used in the mapping of contractile protein structure by resonance energy transfer.
Epithelial mouse mammary cell line exhibiting normal morphogenesis in vivo and functional differentiation in vitro.
Authors: Danielson K G , Oborn C J , Durban E M , Butel J S , Medina D
Published: May 2006

An epithelial cell line, designated COMMA-1D, was derived from mammary tissue of BALB/c mice in the middle of pregnancy. This line, in continuous cell culture for 12 months, exhibits several characteristics distinctive of normal mammary epithelial cells, including induction of casein synthesis in vitro and normal duct morphogenesis in the cleared mammary fat pads of syngeneic mice. The cells also form domes in high density culture and are positive for keratin intermediate filaments by indirect immunofluorescence. COMMA-1D cells have a near diploid number of chromosomes and do not grow in suspension culture or produce tumors in syngeneic hosts. This cell line should prove useful for studies examining the regulation of normal cellular differentiation of mammary cells as well as transformation of epithelial cells to the preneoplastic and neoplastic phenotypes.
Mutants suppressing in trans chorion gene amplification in Drosophila.
Authors: Orr W , Komitopoulou K , Kafatos F C
Published: May 2006

Two recessive female-sterile mutants, K451 and K1214 , disrupt chorion formation by causing underproduction of all major chorion proteins. We present evidence that this effect is due to underaccumulation of the chorion mRNAs and that, in turn, this is caused by a substantial reduction in the level of chorion gene amplification. The mutants are X-linked but located at two sites far from the chorion gene cluster at 7F1 -2; their effect is even more pronounced on the third chromosome chorion gene cluster, and thus the wild type gene must act in trans. The time course of amplification in mutant and wild-type follicles is documented.
Eocytes: a new ribosome structure indicates a kingdom with a close relationship to eukaryotes.
Authors: Lake J A , Henderson E , Oakes M , Clark M W
Published: May 2006

Ribosomal large and small subunits are organized in four general structural patterns. The four types are found in ribosomes from eubacteria, archaebacteria, eukaryotes, and a group of sulfur-dependent bacteria ( eocytes ), respectively. All four ribosomal types share a common structural core, but each type also has additional independent structural features. The independent features include the eukaryotic lobes and the archaebacterial bill on the smaller subunit. On the larger subunit, they include the eocytic lobe, eocytic gap, and eocytic bulge and a modified central protuberance. These data are most parsimoniously fit by a single unrooted evolutionary tree. In this tree eocytes are closely related to eukaryotes, while archaebacteria and eubacteria are closest neighbors. The tree is consistent with currently known molecular biological properties and indicates that eocytes have a phylogenetic importance equal to that of the three known kingdoms. When other properties and molecular mechanisms of these organisms are better defined, we suggest that an appropriate kingdom name for this group would be the Eocyta .
A monoclonal anti-DNA antibody also binds to cell-surface protein(s).
Authors: Jacob L , Tron F , Bach J F , Louvard D
Published: May 2006

A murine monoclonal anti-DNA antibody ( PME77 ) has been found to bind tightly to the plasma membrane of Raji cells. We show here that this monoclonal anti-DNA antibody reacts in a radioimmunoassay with the cell surface of a variety of mammalian cell types and that the antigenic determinant recognized by the monoclonal anti-DNA antibody at the surface of Raji cells is resistant to DNase. It belongs to polypeptides removed from the cell surface by a mild proteinase K treatment.
Antibodies against gamma-aminobutyric acid: specificity studies and immunocytochemical results.
Authors: Seguela P , Geffard M , Buijs R M , Le Moal M
Published: May 2006

Antibodies against gamma-aminobutyric acid (GABA)-glutaraldehyde-lysine were obtained by using a procedure based upon (i) a high yield of coupling of GABA to protein carriers, (ii) the reduction of the resulting immunoreactive double bonds, and (iii) a protocol of alternative immunizations using different immunogens having in common only the GABA-glutaraldehyde-lysine segment. This strategy led to the use of the resulting GABA antiserum without further purification. Specificity controls have been carried out with a radiolabeled ligand, [3H]GABA-glutaraldehyde- prolylphenylalanyl -lysine , which mimicked the structure of the immunogen and the fixed hapten in the tissue. Displacement curves showed that the nearest coupled analogs, beta-alanine and glycine, cross-react poorly with GABA, requiring 175-fold or 795-fold higher concentrations, respectively. Immunocytochemical results indicated that the localization obtained with this GABA antiserum largely corresponds with that reported after glutamate decarboxylase immunocytochemistry. The approach may have general applicability to other small molecules such as amino acids.
Artificial selection for a secondary sexual character in males of
Drosophila silvestris
from Hawaii
Authors: Carson Hampton L. , Teramoto Linden T.
Published: May 2006

Drosophila silvestris
is endemic to the rain forests of Hawaii Island. In populations from the northeast side, the male foreleg tibia bears about 100 long cilia; these are used as a brush to stimulate the female during courtship. Cyclical family selection for high and low cilia number was carried out on progeny of lines started from single wild isofemales collected at a single site. Significant response in both directions was obtained; in the third generation the lines differed by a mean of 25 cilia. Despite much effort to save them, both lines died out without further advance; the low cilia number line died after five and the high cilia number line died after nine generations. The data are compatible with the view that the cilia character is polygenic and is maintained in nature by a stabilizing sexual selection that also favors a polygenic heterozygous state. Although selection in these experiments resulted in dysgenesis, such a result is not inevitable. Disorganization and reorganization of such a genetic system following a population bottleneck might be important as a predisposing condition for the emergence of a specifically novel and possibly isolating mode of courtship.
Chaotic motion of a weakly nonlinear, modulated oscillator
Authors: Miles John
Published: May 2006

A weakly nonlinear oscillator of natural frequency ω
0
and damping ratio δ is driven by an amplitude-modulated force of dimensionless amplitude ε, carrier frequency ω, and modulation frequency ω
1
. Each of (ω - ω
0
)/ω
0
, ω
1
/ω
0
, and δ is O(ε
2/3
) as ε → 0. The response in this resonant neighborhood is a slowly modulated sine wave, the envelope of which is described by three first-order, autonomous, ordinary differential equations. This envelope, which is periodic for δ >> ε
2/3
, is chaotic in certain ranges of (ω - ω
0
)/ω
0
and ω
1
/ω
0
if δ/ε
2/3
is sufficiently small.
Molecular organization of the HLA-SB region of the human major histocompatibility complex and evidence for two SB beta-chain genes.
Authors: Gorski J , Rollini P , Long E , Mach B
Published: May 2006

The class II products of the major histocompatibility complex, also called Ia antigens, are composed of two polypeptide chains, the alpha and beta chains, both encoded within the major histocompatibility complex. In man, the class II antigens can be divided into three biochemically distinct groups called HLA-DR, HLA-DC, and HLA-SB. Our isolation of cDNA clones for the polymorphic beta chain of HLA-DR and HLA-DC has allowed us to study the organization of the class II genes. Here we identify the HLA-SB beta-chain gene in recombinant clones from a cosmid library generated from a consanguineous homozygous B-cell line. The SB beta-chain gene is linked to the SB alpha-chain gene and the two genes are in opposite orientation. A second SB beta-chain gene, corresponding to a new SB beta II locus, has also been identified and cloned. The SB beta-chain genes show much less allelic restriction site polymorphism than the genes for the beta chains of HLA-DR or HLA-DC.
Hydroxymethyluracil DNA glycosylase in mammalian cells.
Authors: Hollstein M C , Brooks P , Linn S , Ames B N
Published: May 2006

An activity has been purified 350-fold from extracts of mouse plasmacytoma cells that forms 5-hydroxymethyluracil (alpha-hydroxythymine) and apyrimidinic sites with phage SPO1 DNA, which contains this base in place of thymine. This DNA glycosylase presumably functions to eliminate hydroxymethyluracil, a major thymine-derived DNA lesion produced by ionizing radiation and oxidative damage. The enzyme has no cofactor requirement and is active in EDTA. Neither intermediate formation nor hydrolysis of hydroxymethyl-deoxyuridine or hydroxymethyldeoxyuridine monophosphate was detected. The enzyme does not cleave apyrimidinic sites in DNA. It does release uracil from the uracil-containing DNA of phage PBS2, but this activity is less than 2% of the predominant uracil DNA glycosylase activity of the cell, which is separated by phosphocellulose chromatography. The major uracil DNA glycosylase does not release hydroxymethyluracil from SPO1 DNA. The hydroxymethyluracil glycosylase is also separated upon phosphocelluose chromatography from a thymine glycol DNA glycosylase activity that is accompanied by an apyrimidinic endonuclease activity.
Insulin activates the appearance of insulin-like growth factor II receptors on the adipocyte cell surface.
Authors: Oka Y , Mottola C , Oppenheimer C L , Czech M P
Published: May 2006

To evaluate the mechanism of insulin action to increase rat 125I-labeled insulin-like growth factor II (125I-IGF-II) binding to rat adipocytes, we raised a potent rabbit antiserum against purified IGF-II receptors from rat placental membranes. The antiserum elicited a positive reaction at a 1:5000 dilution against purified IGF-II receptor in an ELISA and markedly inhibited 125I-IGF-II binding to adipocyte plasma membranes when added prior to the growth factor. Immunoprecipitation lines formed between agar plate wells containing antiserum versus IGF-II receptor, both in the presence and absence of 1 microM IGF-II, indicating that binding of anti-receptor Ig to the IGF-II receptor is not affected by occupancy of the IGF-II binding site. Intact adipocytes treated with or without insulin were incubated with anti-IGF-II receptor Ig, washed, and further incubated with 125I-labeled goat anti-rabbit IgG to monitor the amount of anti-receptor Ig bound. Insulin induced parallel increases in anti-IGF-II receptor Ig binding (2.4-fold) and 125I-IGF-II binding (3-fold) to the isolated cells. The dose-response relationship of insulin action on 125I-IGF-II binding and anti-receptor Ig binding was essentially identical with a half-maximal effect at approximately 0.07 nM insulin. That insulin does not act to expose new types of antigenic sites on IGF-II receptors was indicated by the demonstration that control adipocytes could readily adsorb the anti-receptor Ig. These data demonstrate that increased numbers of IGF-II receptors are displayed in an exposed position on the adipocyte cell surface in response to insulin.
Induction of specific Escherichia coli genes by sublethal treatments with alkylating agents.
Authors: Volkert M R , Nguyen D C
Published: May 2006

Fusions of the lac operon to genes induced by treatment with sublethal levels of alkylating agents have been selected from random insertions of the Mu-dl(ApRlac) phage by screening for induction of beta-galactosidase activity in the presence of methyl methanesulfonate. Genetic analysis reveals that these fusions resulted from insertion of Mu-dl(ApRlac) into two regions of the chromosome. One region (aidA) is near his and, based on phenotypic effects, appears to represent insertion into the alkA gene. The other region (aidB) is in the 92.3- to 98-min region, which harbors no previously identified genes involved in repair of alkylation damage. The aidB fusions caused increased resistance to alkylating agents and caused little or no change in the biological effects of adaptation to alkylating agents. Unlike the aidA fusions, aidB fusions showed increased beta-galactosidase activity in untreated cells in a growth phase-dependent fashion. The ada-5 mutation, which blocks expression of the adaptive response, decreased induction of beta-galactosidase activity in both aidA and aidB fusions after alkylation treatments. Thus, both aidA and aidB share with adaptive response a common regulatory mechanism involving the ada gene. The growth phase-dependent control of the aidB fusions, however, is unaffected by ada, suggesting that a second regulatory mechanism exists that controls only aidB.
Structural relationships among genes that control development: sequence homology between the Antennapedia, Ultrabithorax, and fushi tarazu loci of Drosophila.
Authors: Scott M P , Weiner A J
Published: May 2006

Genes that regulate the development of the fruit fly Drosophila melanogaster exist as tightly linked clusters in at least two cases. These clusters, the bithorax complex (BX-C) and the Antennapedia complex (ANT-C), both contain multiple homoeotic loci: mutations in each locus cause a transformation of one part of the fly into another. Several repetitive DNA sequences, including at least one transposon, were mapped in the ANT-C. DNA from the 3' exon of Antennapedia (Antp), a homoeotic locus in the ANT-C, hybridized weakly to DNA from the 3' exon of Ultrabithorax (Ubx), a homoeotic locus in the BX-C. DNA from each of these 3' exons also hybridized weakly to DNA from the fushi tarazu locus of the ANT-C. The fushi tarazu (ftz) locus controls the number and differentiation of segments in the developing embryo. Sequence analysis of the cross-hybridizing DNA from the three loci revealed the conservation of predicted amino acid sequences derived from coding parts of the genes. This suggests that two homoeotic loci and a "segment-deficient" locus encode protein products with partially shared structures and that the three loci may be evolutionarily and functionally related.
Properties of retrovirus-like particles produced by a human breast carcinoma cell line: immunological relationship with mouse mammary tumor virus proteins.
Authors: Keydar I , Ohno T , Nayak R , Sweet R , Simoni F , Weiss F , Karby S , Mesa-Tejada R , Spiegelman S
Published: May 2006

Clonal derivatives 8 and 11 of the T47D human breast carcinoma cell line release particles that have the biochemical characteristics of a retrovirus. Particles recovered from cultures of [3H]uridine-labeled clone 11 had a density of 1.18 g/ml and contained 60-70S and 35S RNAs associated with reverse transcriptase activity. The production of these particles was steroid-dependent. Clone 8 particles had a higher density, 1.195 g/ml, and their production was independent of steroid hormone. By RIA, antigens crossreactive with the 52,000-dalton envelope glycoprotein gp52, the major external protein of mouse mammary tumor virus, were found associated with these particles and in the media. Most of the gp52-related antigen was in soluble form, but it was enriched in the particle preparation. A lesser amount of antigen was distributed within the cultured cells. Absorption of rabbit antibody to gp52 with clone 11 particle preparations eliminated the ability of this antibody to detect immunocytochemically a crossreactive antigen previously localized in tissue sections of human breast carcinoma. These results indicate that the particle isolates from T47D contain the same gp52-related antigen found in human breast carcinomas and constitute an excellent source for the purification and characterization of this antigen.
Solubilization and characterization of thyrotropin-releasing hormone receptors from rat brain.
Authors: Johnson W A , Nathanson N M , Horita A
Published: May 2006

The thyrotropin-releasing hormone receptor from rat brain was solubilized in a stable unbound form. The natural glycoside digitonin was the only detergent of a variety tested capable of solubilizing the active receptor. The digitonin-solubilized receptor exhibited binding kinetics for 3-[3H]methylhistidine thyrotropin-releasing hormone virtually identical to membrane preparations and responded with a similar order of potency to a series of thyrotropin-releasing hormone analogues that inhibit binding of the labeled ligand. Gel filtration analysis and sucrose density gradient centrifugation indicated a Stokes radius of 5.2 nm, a sedimentation coefficient of 11.2 s, and a corresponding calculated molecular weight of 244,000 for the detergent-receptor complex. The soluble receptor shows a gradual loss of binding activity over 48 to 72 hr when kept at 4 degrees C. However, the preparation may be frozen at -20 degrees C with no significant loss of activity.
New protein kinase from plasma membrane of Ehrlich ascites tumor cells activated by natural polypeptides.
Authors: Racker E , Abdel-Ghany M , Sherrill K , Riegler C , Blair E A
Published: May 2006

A polypeptide-dependent protein kinase was purified about 80-fold from an extract of plasma membranes of Ehrlich ascites tumor cells. The membranes were extracted with Nonidet P-40, and the extract was purified by ammonium sulfate fractionation and hydroxylapatite and affinity chromatography. The activity was stimulated 10-fold or more by polypeptide preparations from a variety of tissues, including placenta and hypothalamus. Polypeptide-dependent protein kinase had a pH optimum of about 7.5 and required Mg2+ for activity. Mn2+ at low concentrations (200 microM) stimulated enzyme activity somewhat but inhibited activity strongly at higher concentrations. The best available substrate for polypeptide-dependent protein kinase was beta-casein, and little or no phosphorylation was observed with alpha-casein, kappa-casein, phosvitin, alpha-lactalbumin, alpha-lactoglobulin, and histone. However, several endogenous substrates from plasma membranes of Ehrlich ascites tumor cells were phosphorylated. Polypeptide-dependent protein kinase activity was not inhibited by 10 mM N-ethylmaleimide, and this resistance was useful in differentiating this protein kinase from other protein kinases that were present in crude fractions and sensitive to the inhibitor.