bluuebunny/crossref_metadata_2025 huggingface dataset:
Sites of sequence variability in Epstein-Barr virus DNA from different sources.
Authors: Rymo L , Lindahl T , Adams A
Published: May 2006

The intracellular Epstein-Barr virus (EBV) DNA present in virus-transformed cells was partly purified from 23 cell lines or biopsies of Burkitt lymphoma, nasopharyngeal carcinoma, infectious mononucleosis, or healthy carrier origin. Such DNA was cleaved in fragments (A-K) of molecular weights between 1 x 10(6) and 30 x 10(6) with restriction enzyme EcoRI, and these fragments were analyzed by standard methods involving agarose gel electrophoresis, transfer to nitrocellulose filters, and hybridization with radioactive EBV DNA or complementary RNA. Sequence variability among different EBV DNA isolates was largely confined to the A, C, and I fragments. These results are discussed in relation to the linkage map of the EcoRI fragments of EBV DNA. The EcoRI cleavage pattern of intracellular viral DNA of an EBV-like virus from baboon cells, Herpesvirus papio, was entirely different from that of human EBV isolates.
Structural evidence for independent joining region gene in immunoglobulin heavy chains from anti-galactan myeloma proteins and its potential role in generating diversity in complementarity-determining regions
Authors: Rao D. Narayana , Rudikoff Stuart , Krutzsch Henry , Potter Michael
Published: May 2006

We have determined the variable region sequences of four heavy chains from β(1-6)D-galactan-binding myeloma proteins. Two of these proteins are identical to position 100 which is located in the third complementarity-determining region (CDR-3). The remaining two differ at a total of 8 positions over the first 100 amino acids, and all of the differences can be explained by single-base mutations at the DNA level. When an assessment is made of the protein segment following CDR-3, which has been termed “J segment” or “FR4,” a completely different pattern of variation is observed. The J segments from the four proteins can be divided into two sets. Members of each set share a series of linked amino acids not found in members of the alternative set. The two proteins identical to position 100 have J segments from the two different sets, suggesting that recombination has occurred between
V
and
J
genes. An examination of the CDR-3 sequences from the four heavy chains reveals substitutions at positions 100 and 105. Gly is found at 100 in two of the proteins and His in the remaining two. In the two proteins with Gly-100, the following J sequence is limited to one of the two sets of J segments defined by linked amino acids. Similarly, the two heavy chains with His-100 have J segments from the second set. Thus, at the protein level an apparent association is seen between CDR-3 and J segment. If CDR-3 should be found linked to J segment at the DNA level, a new mechanism would be introduced for increasing antibody diversity by recombining various
CDR-3
plus
J
genes with genes coding for the remainder of the variable region. Alternatively, if CDR-3 were coded for by the
V
gene, then the recombination of
V
with
J
may provide an opportunity to introduce mutations in
CDR-3
. In this case the linkage of amino acids in CDR-3 and the J segments would suggest that recognition signals are used such that certain
V
genes only pair with a given
J
gene.
Neodymium isotopes in flood basalts from the Siberian Platform and inferences about their mantle sources
Authors: DePaolo D. J. , Wasserburg G. J.
Published: May 2006

The initial isotopic compositions of Nd and Sr in basalts from the Central Siberian Plateau and other major continental flood basalts are reported. The continental flood basalts appear to be the product of partial melting of mantle sources that consist of relatively primitive undifferentiated material and are clearly distinct from midocean ridge basalts, which sample mantle reservoirs that have been modified by extraction of continental crust earlier in earth history. These observations provide fundamental constraints on models of mantle structure and dynamics. Isotopic effects of crustal contamination are clearly recognizable in some continental flood basalts, but these effects can be distinguished from isotopic patterns inherited from the mantle magma sources.
L-glucosylceramide: synthesis, properties, and resistance to catabolism by glucocerebrosidase in vitro.
Authors: Gal A E , Pentchev P G , Massey J M , Brady R O
Published: May 2006

Procedures for the synthesis and radioactive labeling of L-glucosylceramide are described. This compound is a stereoisomeric analogue of D-glucosylceramide which occurs in nature and accumulates in pathological quantity in the organs and tissues of patients with Gaucher disease. The properties of L-glucosylceramide that have been examined so far have been found to be indistinguishable from those of the naturally occurring glycolipid. However, L-glucosylceramide is completely refractory to enzymatic hydrolysis by purified placental glucocerebrosidase and enzyme(s) present in whole tissue extracts. It is anticipated that L-glucosylceramide will be a uniquely useful substance for exploring pathogenetic processes in animal analogues of Gaucher disease.
Binding of ribosomes to 5'-terminal leader sequences of eukaryotic messenger RNAs.
Authors: Filipowicz W , Haenni A L
Published: May 2006

Tobacco mosaic virus and turnip yellow mosaic virus genome RNAs, which have long (greater than or equal to 69 nucleotides) 5'-terminal leader sequences preceding the AUG initiation codon, can form disome initiation complexes when incubated with a wheat germ extract and sparsomycin. In tobacco mosaic virus RNA, whereas one ribosome in such complexes presumably occupies the AUG-containing initiation site, the other is located within the RNA leader sequence. The results favor a model of eukaryotic initiation in which ribosomes first bind to the 5' end of the mRNA independently of AUG, then advance to the AUG initiation codon, where protein synthesis ensues.
Coupling of the glucagon receptor to adenylyl cyclase by GDP: evidence for two levels of regulation of adenylyl cyclase.
Authors: Iyengar R , Birnbaumer L
Published: May 2006

In rat liver plasma membranes preactivated with guanosine 5'-[beta,gamma-imido[triphosphate (GuoPP[NH]P), GDP promoted coupling of occupied glucagon receptor to adenylyl cyclase [adenylate cyclase; ATP, pyrophosphate-lyase (cyclizing), EC 4.6.1.1] with an apparent association constant Ka of 0.1-0.15 microM. The apparent Ka for the same effect of GTP was 0.2 microM. The effect of GDP was shown not to be due to GTP formed by putative transphosphorylation reaction(s) when ATP was present in the assay as substrate. In membranes not preactivated with GuoPP[NH]P, GDP both competitively inhibited GuoPP[NH]P stimulation of adenylyl cyclase (Ki 0.10 microM) and supported stimulation of cyclizing activity (apparent Ka 0.10 microM) by glucagon. These effects of GDP occurred in the absence of added GTP and in the absence of sufficient formation of GTP by putative transphosphorylation reaction(s) to account for them. It is concluded that two levels of regulation of liver adenylyl cyclase (cyclizing) activity must exit. One level is termed "receptor regulation"; it depends on occupancy of a receptor-related R site by nucleotide and is specific for either GDP or GTP. The second level of regulation is termed "GTPase regulation"; it is inhibited by GDP, depends on both GTP and GTPase, and accounts for activation of cyclizing activity by nonhydrolyzable analogs of GTP. The data suggest that both levels of regulation coexist and may synergize, one mediating responses to stimuli external to the cell (receptor regulation) and the other mediating stimuli of intracellular origin (GTPase regulation).
Theoretical methods for study of kinetics of models of the mitochondrial respiratory chain.
Authors: Hill T L , Chay T R
Published: May 2006

In earlier work, Hill and Chance obtained exact steady-state kinetic properties for partial models of the mitochondrial respiratory chain with two isopotential pools and one four-state "site enzyme" between the two pools. That work is extended here to full models of the respiratory chain with four isopotential pools and three four-state site enzymes between pairs of pools. Because of the complexity of the model, exact calculations are no longer possible. Instead, we show, by means of some examples, the feasibility of using Monte Carlo calculations on all cases and numerical solution of thousands of kinetic differential equations in many cases.
Developmental and mutational changes of glycoproteins in the mouse neuronal retina: studies with bovine galactosyltransferase.
Authors: Wallenfels B
Published: May 2006

Bovine galactosyltransferase (lactose synthase; EC 2.4.1.22) which catalyzes the transfer of galactose from UDPgalactose to glycoproteins with N-acetylglucosamine as the terminal residue of their oligosaccharide side chains was used to label glycoproteins of mouse retina with [14C]galactose. The glycoproteins were separated by isoelectric focusing in the first dimension and by sodium dodecyl sulfate gel electrophoresis in the second dimension. Their position on the gel was determined by autofluorography. With this method, quantitative as well as qualitative changes in the glycoprotein composition of the neuronal mouse retina during postnatal development were observed. Furthermore, it was found that the photoreceptor loss in mice with retinal degeneration was paralleled by the disappearance of certain glycoprotein bands.
Initiator tRNAs have a unique anticodon loop conformation.
Authors: Wrede P , Woo N H , Rich A
Published: May 2006

Transfer RNA (tRNA) molecules have been labeled with 32P at the 5' end and subjected to S1 nuclease digestion. The products were analyzed by high-resolution gel electrophoresis. Three initiator tRNAs and six chain-elongating tRNAs were examined. S1 nuclease cleaved Escherichia coli tRNAfMet, yeast tRNAfMet, and mammalian tRNAfMet at the same two positions in the anticodon loop. In contrast, S1 nuclease cleaved the anticodon loop of E. coli tRNAmMet, yeast tRNAmMet, yeast tRNAPhe, Schizosaccharomyces pombe tRNAPhe, E. coli tRNA2Glu, and E. coli tRNATrp (su+) at four positions generally, except where a modified nucleotide in the wobble position inhibited the enzyme. The marked contrast between these cleavage patterns suggests a different conformation for the anticodon loops of these two classes of tRNA molecules. It is suggested that the specialized conformation in the anticodon loop of initiator tRNAs may be due to a special sequence of GC base pairs in the adjoining anticodon stem.
Molecular cloning and partial characterization of delta-crystallin cDNA sequences in a bacterial plasmid.
Authors: Bhat S P , Piatigorsky J
Published: May 2006

Double-stranded cDNA synthesized from delta-crystallin mRNA isolated from lens fiber cells of 15-day-old embryonic chicken was cloned in Escherichia coli chi 1776 in the Pst I site of the plasmid pBR322 by using the oligo(dC) . oligo(dG) joining procedure. Twelve Amps Tetr transformants contained sequences complementary to purified delta-crystallin [32P]cDNA. One of the recombinant clones (p delta Cr-2) had an insert of 1241 +/- 240 base pairs, as judged by R-looping analysis with purified delta-crystallin mRNA. The inserted cDNA represents at least 69% of the delta-crystallin coding sequences. p delta Cr-2 was further characterized by restriction analysis, protection of delta-crystallin [3H]cDNA from digestion by S1 nuclease, and hybrid-mediated arrest of delta-crystallin mRNA translation in vitro. p delta Cr-2 provides an invaluable probe for additional analysis of the primary structure, gene organization, and regulated synthesis of delta-crystallin, the principal protein synthesized during lens differentiation in the chicken embryo.
Equivalence of maximizing reproductive value and fitness in the case of reproductive strategies
Authors: Schaffer William M.
Published: May 2006

The proposed equivalence of maximizing reproductive value and fitness is examined for two model life histories. In the first instance, it is assumed that offspring are fledged before the start of the next breeding season. In this case the proposed equivalence is verified. In the second model, parents care for their progeny for more than 1 year. In this case the optimal reproductive expenditure at a particular age is shown to depend on both current reproductive value and the diminution in survival rates of previously conceived young still dependent on parental protection.
Nick-free formation of reciprocal heteroduplexes: a simple solution to the topological problem.
Authors: Wilson J H
Published: May 2006

Because the individual strands of DNA are intertwined, formation of heteroduplex structures between duplexes--as in presumed recombination intermediates--presents a topological puzzle, known as the winding problem. Previous approaches to this problem have assumed that single-strand breaks are required to permit formation of fully coiled heteroduplexes. This paper describes a simple, nick-free solution to the winding problem that satisfies all topological constraints. Homologous duplexes associated by their minor-groove surfaces can switch strand pairing to form reciprocal heteroduplexes that coil together into a compact, four-stranded helix throughout the region of pairing. Model building shows that this fused heteroduplex structure is plausible, being composed entirely of right-handed primary helices with Watson-Crick base pairing throughout. Its simplicity of formation, structural symmetry, and high degree of specificity are suggestive of a natural mechanism for alignment by base pairing between intact homologous duplexes. Implications for genetic recombination are discussed.
Subunit interaction during catalysis: alternating site cooperativity in photophosphorylation shown by substrate modulation of [18O]ATP species formation.
Authors: Hackney D D , Rosen G , Boyer P D
Published: May 2006

Pronounced substrate modulation of incorporation of water oxygen into ATP formed by photophosphorylation is observed, as measured by 31P NMR analysis of products formed from ADP and highly 18O-labeled Pi. A marked increase occurs in oxygen exchange per ATP formed as ADP or Pi concentration is decreased. This is explainable by the binding-change mechanism for ATP synthesis, in which the energy-linked release of ATP from one site requires the binding of ADP and Pi at an alternate site. Analysis of the distribution of 18O-labeled species arising from the ATP formed eliminates explanations for substrate modulation based on preexisting or induced enzyme heterogeneity. Furthermore, the results, together with other related findings, make participation of control sites unlikely. The occurrence of alternating site catalysis cooperativity in ATP synthesis by chloroplasts thus appears to be reasonably well established.
beta-Endorphin: formation of alpha-helix in lipid solutions.
Authors: Wu C S , Lee N M , Loh H H , Yang J T , Li C H
Published: May 2006

Human beta-endorphin adopts a partial helical conformation in aqueous solutions of cerebroside sulfate, ganglioside GM1, phosphatidylserine, and phosphatidic acid, but not of cerebroside and phosphatidylcholine, as evidenced by circular dichroic spectra. Addition of Ca2+ to the peptide in cerebroside sulfate solution can break up the helix; at 10 mM Ca2+ the peptide (12 microM) essentially exists in an unordered form. For comparison, sheep beta-lipotropin in acidic cerebroside sulfate solution (pH less than 4) also has a partial helical conformation of the complex between human beta-endorphin and lipids may be related to the opiatelike function of this peptide hormone.
Human leukocyte interferon: Relationship between molecular structure and species specificity
Authors: Thang M. N. , Thang D. C. , Chelbi-Alix M. K. , Robert-Galliot B. , Commoy-Chevalier M. J. , Chany C.
Published: May 2006

Human leukocyte interferon can be separated into two classes of subspecies by polynucleotide-agarose affinity chromatography; 30-40% of the molecular species have the polynucleotide-binding property and 60-70% lack affinity for the polynucleotide ligand. When analyzed on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, the former class of interferon has a slower mobility corresponding to the migration of a polypeptide of 21,000 daltons, while the latter class has a faster mobility corresponding to a polypeptide of 13,500-15,000 daltons. By analogy to the behavior of other interferons and a class of nucleotidyl transferases on the polynucleotide-agarose chromatography, we suggest that the human leukocyte interferon having the polynucleotide-binding site is in a possibly “native” conformation and the loss of affinity for polynucleotide results from a degradative alteration of the native molecules. Moreover, the alteration of interferon is accompanied by an increase in heterospecific activity on bovine cells. It is suggested that the polypeptide domain responsible for species specificity may be closely related to the polynucleotide binding area. The modified interferon molecule, however, still conserves its antiviral activity. The simplicity and the high capacity of polynucleotide-agarose chromatography make this a powerful technique for the purification of interferon. The easy separation of these two classes of human leukocyte interferon makes the purification procedures more rational and will facilitate the preparation of both subspecies to a high degree of molecular homogeneity.
Cloning of the active thymidine kinase gene of herpes simplex virus type 1 in Escherichia coli K-12.
Authors: Colbere-Garapin F , Chousterman S , Horodniceanu F , Kourilsky P , Garapin A C
Published: May 2006

A herpes simplex virus DNA fragment that is produced by digestion with BamHI endonuclease and carries the thymidine kinase (TK; ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) gene has been cloned in Escherichia coli. A recombinat plasmid, pFG5, has been analyzed extensively and a detailed restriction map is presented. pFG5 DNA efficiently transforms TK- mouse L cells. The TK coding sequence in the cloned fragment has been localized and a smaller recombinant plasmid, pAG0, also carrying an active TK gene, has been constructed to serve as a more convenient vector for transfer, into TK- cells, of genes previously cloned in E. coli.
Ribosome structure: localization of 3' end of RNA in small subunit by immunoelectronmicroscopy.
Authors: Olson H M , Glitz D G
Published: May 2006

The 3' end of the RNA in the 30S ribosomal subunit of Escherichia coli has been modified by oxidation with sodium periodate and conjugation with the (mono) dinitrophenyl derivative of ethylenediamine. Antibodies, induced with dinitrophenyl-bovine serum albumin, interact with the modified ribosomal subunits. Electron micrographs of negatively stained antibody-subunit complexes show individual ribosomal subunits to which a single antibody molecule is bound and subunit dimers cross-linked by an IgG molecule. The modified 3' terminus has been localized to a single site on the upper portion of the platform region of the 30S subunit. This location is consistent with earlier placements of proteins that react with the 3' end of the RNA.
Characterization of the iron-sulfur centers in succinate dehydrogenase.
Authors: Coles C J , Holm R H , Kurtz D M , Orme-Johnson W H , Rawlings J , Singer T P , Wong G B
Published: May 2006

Two techniques have been applied to the determination of the number and type (2-Fe, 4-Fe) of iron-sulfur centers in the iron-sulfur flavoprotein succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1]. One procedure uses p-CF3C6H4SH as an extrusion reagent and Fourier transform 19F nuclear magentic resonance as the method of detection and quantitation of extruded cores of these centers in the form of [Fe2S2(SRF)4]2- and [Fe4S4(SRF)4]2- (RF = p-C6H4CF3). The second procedure, interprotein core transfer, involves thiol displacement of iron-sulfur cores followed by specific core transfer to the apoproteins of Bacillus polymyxa ferredoxin and adrenodoxin. Detection and quantitation are accomplished by electron paramagnetic resonance of reduced proteins at low temperatures. Both procedures clearly show that succinate dehydrogenase contains two dimeric (Fe2S2) and one tetrameric (Fe4S4) centers per mole of histidyl flavin, accounting for all eight nonheme iron and eight labile sulfur atoms found by chemical analysis. These results remove uncertainties created by the less than stoichiometric amounts of binuclear centers detected by electron paramagnetic resonance after dithionite reduction and provide secure characterization of the iron-sulfur centers in this enzyme.
Transcription of spacer sequences in genes coding for ribosomal RNA in Xenopus cells.
Authors: Rungger D , Achermann H , Crippa M
Published: May 2006

Untreated Xenopus cells synthesize RNA is increased and some sequences complementary to those of the nontranscribed spacer are found in the heavy shoulder of the 40S precursor rRNA peak. In such events transcription initiation seems to take place within the spacer because its middle and right BamHI endonuclease fragments are preferentially transcribed, whereas only few RNA sequences complementary to the left spacer fragment are found. It is concluded that at least some spacer regions contain promoters for transcription and can be transcribed either into a special class of "spacer transcripts" or into molecules covalently linked to rRNA precursor.
Identification and characterization of a self-regulated repressor of translocation of the Tn3 element.
Authors: Chou J , Casadaban M J , Lemaux P G , Cohen S N
Published: May 2006

Gene fusions that bring expression of the lacZ gene under control of transcriptional and trnaslational signals within the transposable element Tn3 have been used to study regulation of Tn3-specified proteins. A gene encoding a 21,355-Mr peptide that represses translocation of Tn3 and acts at the level oquenced; amber, missense, and cis-dominant (operator-constitutive) point mutations in this gene have been isolated and characterized.
Biogenesis of poxviruses: role for the DNA-dependent RNA polymerase II of the host during expression of late functions.
Authors: Silver M , McFadden G , Wilton S , Dales S
Published: May 2006

The participation of host RNA polymerase II in the vaccinia life cycle was examined by comparing efficiency of multiplication after treating the Ama+ sensitive and Ama 102 drug resistant lines with alpha-amanitin. In the latter, resistance is due to a mutation in RNA polymerase II. The toxin profoundly reduces synthesis of virus-specified polypeptides and morphopoeisis in Ama+ but not in Ama 102 rat myoblasts without appreciably altering vaccinia DNA replication in either cell type. This implicates RNA polymerase II in the expression of late virus functions. Circumstantial evidence from a model system indicates that gamma irradiation of the host prior to infection might disrupt transcription into functional mRNA from the nucleus. Irradiation does not, however, alter the capability of the host to support vaccinia multiplication fully. Therefore, ongoing host nuclear transcription may not be required by this virus. The above results are consistent with the ability of cytoplasts to produce small quantities of mature progeny. Our studies lead us to hypothesize that RNA polymerase II or a subunit of the host enzyme may participate directly in late transcription of the vaccinia genome.
Cholinergic activity regulates muscarinic receptors in central nervous system cultures.
Authors: Siman R G , Klein W L
Published: May 2006

Muscarinic acetylcholine receptor activation induces a loss of muscarinic receptors from cultured neuroblastoma and embryonic chicken cerebrum cells. As measured by specific binding of [3H]quinuclidinyl benzilate, steady-state receptor concentrations decrease 75% in response to receptor-saturating concentrations of cholinomimetic drugs. Both the degree and duration of activation determine the extent of receptor loss. A method for analyzing receptor turnover, which does not rely upon protein synthesis inhibitors, shows that activated receptors have a half-life of 1.6 hr. The regulated rate of receptor disappearance begins as soon as activators are added, and the rate is maintained as long as activators are present. The receptor blocker atropine causes an increase in receptor levels in central nervous system cultures but has no effect on receptors in cultures of adrenergic neuroblastoma cells. Because spontaneous cholinergic activity is expected only in the central nervous system cultures, the increase likely reflects blockade of endogenous regulation. Cytochalasin B blocks receptor regulation, suggesting that regulation may be mediated by a process involving microfilaments.
Ligated chlorophyll cation radicals: Their function in photosystem II of plant photosynthesis
Authors: Davis M. S. , Forman A. , Fajer J.
Published: May 2006

Magnesium tetraphenylchlorin, a synthetic model for chlorophyll, exhibits significant variations in the unpaired spin densities of its cation radicals with concomitant changes in oxidation potentials as a function of solvent and axial ligand. Similar effects are observed for chlorophyll (Chl) a and its cation radicals. Oxidation potentials for Chl → Chl
+.
as high as +0.9 V (against a normal hydrogen electrode) are observed in nonaqueous solvents, with linewidths of the electron spin resonance signals of monomeric Chl
+.
ranging between 9.2 and 7.8 G in solution. These changes in electronic configuration and ease of oxidation are attributed to mixing of two nearly degenerate ground states of the radicals theoretically predicted by molecular orbital calculations. Comparison of the properties of chlorophyll
in vitro
with the optical, redox, and magnetic characteristics attributed to
P
-680, the primary donor of photosystem II which mediates oxygen evolution in plant photosynthesis, leads us to suggest that
P
-680 may be a ligated chlorophyll monomer whose function as a phototrap is determined by interactions with its (protein?) environment.
Conformation of gramicidin A channel in phospholipid vesicles: a 13C and 19F nuclear magnetic resonance study.
Authors: Weinstein S , Wallace B A , Blout E R , Morrow J S , Veatch W
Published: May 2006

We have determined the conformation of the channel-forming polypeptide antibiotic gramicidin A in phosphatidylcholine vesicles by using 13C and 19F NMR spectroscopy. The models previously proposed for the conformation of the dimer channel differ in the surface localization of the NH2 and COOH termini. We have incorporated specific 13C and 19F nuclei at both the NH2, and COOH termini of gramicidin and have used 13C and 19F chemical shifts and spin lattice relaxation time measurements to determine the accessibility of these labels to three paramagnetic NMR probes--two in aqueous solution and one attached to the phosphatidylcholine fatty acid chain9 all of our results indicate that the COOH terminus of gramicidin in the channel is located near the surface of the membrane and the NH2 terminus is buried deep within the lipid bilayer. These findings strongly favor an NH2-terminal to NH2-terminal helical dimer as the major conformation for the gramicidin channel in phosphatidylcholine vesicles.
Yeast chromatin is uniformly digested by DNase-I.
Authors: Lohr D , Hereford L
Published: May 2006

The DNase I (EC 3.1.21.1) sensitivity of transcribed yeast chromatin has been examined. We find that, in contrast to chromatin from higher eukaryotes, transcribed yeast chromatin and total yeast chromatin are equally sensitive to DNase I digestion. We interpret these results to mean that the entire yeast genome exists in a state that represents a restricted proportion of total chromatin in higher eukaryotes.
Cloning of the structural gene (ompA) for an integral outer membrane protein of Escherichia coli K-12.
Authors: Henning U , Royer H D , Teather R M , Hindennach I , Hollenberg C P
Published: May 2006

The gene (ompA) for the major outer membrane protein II* from Escherichia coli K-12 has been cloned on a 5-megadalton EcoRI fragment by using phage lambda as vector. The gene is expressed during the lytic cycle of the recombinant phage and the insoluble membrane-bound protein was detected in phage plaques with a simple radioimmunoassay. Transfer of the EcoRI fragment into plasmid pSC101 and expression in a host lacking protein II* led to overproduction of protein II* and decreased production of two other major outer membrane proteins. Expression of the plasmid pSC101-ompA+ in minicells derived from an ompA minicell-producing strain led to synthesis, at high rates, of this protein and massive accumulation of a second cell envelope protein most likely representing the biosynthetic precursor of protein II*.
Cloning of integrated Moloney sarcoma proviral DNA sequences in bacteriophage lambda.
Authors: Vande Woude G F , Oskarsson M , Enquist L W , Nomura S , Sullivan M , Fischinger P J
Published: May 2006

We have identified integrated proviral DNA sequences of m1 and HT-1 isolates of Moloney sarcoma virus (MuSV) in EcoRI digests of transformed mink cell genomic DNA and have cloned these fragments in bacteriophage lambda. Both the lambda-HT1 phage recombinant, containing a 12.3-kilobase MuSV pair (kb) fragment, and the lambda-m1 phage recombinant, containing a 7.0-kb fragment, possess full copies of the sarcoma viruses along with 5' and 3' host flanking sequences. The MuSV proviral DNA sequences, 6.7 kb for HT-1 and 5.2 kb for m1, are colinear by heteroduplex microscopy with the 1.5-kb difference in size accounted for by two approximately equal to 0.8-kb deleted regions in m1. Both integrated viral genomes are terminally redundant and have integrated at the same site in the provirus but at different sites on the host chromosome. The host sequence flanking integrated HT-1 MuSV have been identified as a single EcoRI restriction fragment of 5.6 kb in normal mink cells.
Stimulation of phospholipid metabolism in embryonic muscle cells treated with phospholipase C.
Authors: Kent C
Published: May 2006

Phospholipid metabolism is dramatically stimulated in cultured myogenic cells in which cell fusion was inhibited with phospholipase C (phosphatidylcholine choline-phosphohydrolase; EC 3.1.4.3). Phospholipase C was active under the culture conditions as shown by the degradation of exogenous phosphatidylcholine. Rates of incorporation of 32Pi and [methyl-3H]choline into lipids were about 5-fold greater in phospholipase-treated cells than in either untreated fusing cells or untreated cells prevented from fusing by calcium deprivation. The greatest stimulation in the phospholipase C-treated cultures occurred with synthesis of phosphatidylcholine and sphingomyelin; synthesis of phosphatidylinositol and cardiolipin was not stimulated. Degradation of cellular [32P]phosphatidylcholine and appearance in the culture medium of the degradation product [32P]phosphocholine were both increased. Levels of total cellular phospholipids and of individual phospholipid classes were similar in control and phospholipase-treated cells. The results suggest that the membrane phospholipid composition in myogenic cells is controlled by a regulatory mechanism which increases the synthesis of phospholipids that are degraded in the presence of the phospholipase.
Isolation of a high molecular weight actin-binding protein from baby hamster kidney (BHK-21) cells.
Authors: Schloss J A , Goldman R D
Published: May 2006

A high molecular weight protein (HMWP) with properties similar to those of both actin-binding protein (ABP) and filamin has been isolated from cultured baby hamster kidney (BHK-21) cells. The protein was present in an actomyosin-depleted sucrose extract of the cells and was eluted, upon gel chromatography on Sepharose 4B, near the void volume. The subunit migration on sodium dodecyl sulfate/polyacrylamide gels and the amino acid composition of HMWP were similar to those of ABP and filamin. HMWP bound to and crosslinked F-actin from rabbit muscle, as shown by the formation of a gel that was sedimented with low-speed centrifugation. This interaction was insensitive to temperature and low concentrations of calcium ions, although it may depend on the presence of myosin. Observation of thin sections of the actin-HMWP gel revealed crosslinked complexes of laterally aggregated actin filaments. The axial period of the dense crosslinks was 34 nm. The HMWP may be involved in regulation of microfilament organization.
Regulation of the tissue specificity of an enzyme by a cis-acting genetic element: evidence from interspecific Drosophila hybrids.
Authors: Dickinson W J , Carson H L
Published: May 2006

Homologous genes for alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) are expressed in qualitatively different patterns during the development of two closely related species of Hawaiian Drosophila. In interspecific hybrids, each parental structural allele is expressed according to the developmental program characteristic of the species from which it is derived. This provides strong evidence for a cis acting control element.
Evidence that a single DNA ligase is involved in replication and recombination in yeast.
Authors: Fabre F , Roman H
Published: May 2006

The possible existence in yeast of different nuclear DNA ligase enzymes led us to ask whether induced recombination (gene conversion) involves the same ligase as that involved in DNA replication. The conditional cdc9 mutant is known to be defective, under restrictive conditions, in the rejoining of Okazaki fragments. We show here that under the same conditions, x-ray-induced convertants within the cdc9 locus are produced with kinetics indicating that most, if not all, of the conversion events require the participation of the cdc9-controlled ligase. Thus, the same DNA ligase is involved in DNA replication and in induced gene conversion.
Apolipoproteins in human cerebrospinal fluid.
Authors: Roheim P S , Carey M , Forte T , Vega G L
Published: May 2006

The presence of apolipoproteins A-I, E, C-II, and C-III and the absence of apolipoprotein B was demonstrated in human cerebrospinal fluid. The concentration of apolipoproteins was measured by electroimmunoassay. Apolipoproteins E, C-II, and C-III were present in cerebrospinal fluid at 3--5% of their concentration in plasma; the cerebrospinal fluid level of apolipoprotein A-I was 0.4%. Most of the cerebrospinal fluid apolipoproteins were present in the rho less than 1.21 g/ml lipoprotein fraction. The major apolipoporteins of cerebrospinal fluid are E and A-I. The possible mechanism of transfer and the physiological and pathophysiological role of apolipoproteins in cerebrospinal fluid are postulated.
Restriction endonuclease cleavage map and location of unique features of the DNA of hepatitis B virus, subtype adw2.
Authors: Siddiqui A , Sattler F , Robinson W S
Published: May 2006

DNA of hepatitis B virus (HBV) of hepatitis B surface antigen (HBsAg) subtype adw2 made fully double stranded by the virion DNA polymerase and radiolabeled either by the virion DNA polymerase reaction or by nick-translation with 32P-labeled deoxynucleoside triphosphates was used to establish a map of restriction endonuclease cleavage sites by the method double and triple enzyme digestion and to determine the relative positions of several unique physical features of this DNA. The five restriction sites for enzyme HincII, the two sites each for BamHI, Ava I, and Bgl II, and the single sites for EcoRI, Pst I, Hpa I, and Taq I were positioned relative to each other. Within this map, the single-stranded region in HBV DNA has been localized and the locations of nicks in each strand (a and b) have been determined with respect to restriction sites on the circular map. Comparison of restriction endonuclease cleavage patterns of DNAs of HBV of HBsAg subtypes adw2, ayw3, and adrq+ revealed consistent differences among subtypes and occasional differences within subtypes.
The Webster method of apportionment
Authors: Balinski M. L. , Young H. P.
Published: May 2006

Several results concerning the problem of U.S. Congressional apportionment are given which, together, indicate that a method first proposed by Daniel Webster (also known as the “Major Fractions” method) seems fairest when judged on the basis of criteria suggested by common sense and precedent.
Restoration of active transport of solutes and oxidative phosphorylation by naphthoquinones in irradiated membrane vesicles from
Mycobacterium phlei
Authors: Lee Soon-Ho , Sutherland Thomas O. , Deves Rosa , Brodie Arnold F.
Published: May 2006

Irradiation of the inverted membrane vesicles of
Mycobacterium phlei
with light at 360 nm inactivated the natural menaquinone [MK
9
(II-H)] and resulted in a loss of substrate oxidation, pH gradient, membrane potential, active transport of proline or calcium ions, and oxidative phosphorylation. Restoration of the protonmotive force and active transport occurred on addition of naphthoquinones such as vitamin K
1
, menadione, or lapachol to the irradiated membrane vesicles. However, coupled phosphorylation was restored only by vitamin K
1
. Menadione and lapachol did not act as uncoupling agents. The magnitude of the pH gradient and membrane potential in the quinone-restored system was a reflection of the rate of oxidation and was correlated with the rate of uptake of proline or Ca
2+
. These results are consistent with the chemosmotic hypothesis proposed for the energy transducing mechanism for active transport and further demonstrate that the complete respiratory chain is not required to drive active transport. In contrast, the data suggest that in addition to the driving force (protonmotive force) necessary to establish oxidative phosphorylation, a specific spatial orientation of the respiratory components, such as the naphthaquinones, is essential for the utilization of the proton gradient or membrane potential or both. Bypass of electrons from the respiratory chain with menadione may explain the inability of this quinone to restore oxidative phosphorylation; however, lapachol restores oxidation by the same electron transport pathway as the natural menaquinone but fails to restore phosphorylation. Because all three quinones restore the protonmotive force, other factors that are discussed must be considered in understanding the mechanism of oxidative phosphorylation.
Mitogenic hormone-induced intracellular message: assay and partial characterization of an activator of DNA replication induced by epidermal growth factor.
Authors: Das M
Published: May 2006

This paper explores the pathway from nuclear quiescence to mitogenesis. It describes an in vitro assay for an activator of DNA replication induced by epidermal growth factor (EGF) in responsive cells. Cytoplasmic extracts from EGF-treated 3T3 cells were found to contain substances that can stimulate DNA synthesis in isolated nuclei from spleen cells of adult frogs. Extracts from untreated resting 3T3 cells lack this activity, and EGF itself is incapable of stimulating DNA synthesis in these cell-free systems. The extract-induced stimulation of incorporation of [3H]dTTP into nuclear DNA is ATP dependent and requires the presence of the four deoxyribonucleoside triphosphates, suggesting the occurrence of replication rather than repair synthesis. This cell-free assay has been used to obtain some initial insights into the mechanism of induction and biochemical characterization of the intermediate in EGF action. Half-maximal induction of the active intracellular substance is achieved at about 0.08 nM EGF, a concentration that correlates well with the concentration required for half-maximal mitogenesis. Studies on the biochemical characteristics of this active substance strongly suggest that the activity is associated with a protein. The activity is nondialyzable and sensitive to trypsin and heat. Sucrose gradient centrifugation of the extract revealed three peaks of activity with molecular weights of 46,000, 110,000, and 270,000 (sedimentation coefficients: 3.7 S, 6.6 S, and 12 S, respectively). These results indicate that receptor-EGF interaction at the cell surface leads to the intracellular generation of protein that are capable of stimulating quiescent nuclei into activity.
Effect of cleaving interchain disulfide bridges on the radius of gyration and maximum length of anti-poly(D-alanyl) antibodies before and after reaction with tetraalanine hapten.
Authors: Pilz I , Schwarz E , Durchschein W , Light A , Sela M
Published: May 2006

The small-angle x-ray scattering of solutions of rabbits IgG antibodies and their derivatives has been investigated. The reduction and alkylation of the native antibody cause a small increase of the molecular parameters, indicating a limited expansion of the molecule. Binding of native antipoly(D-alanyl) antibodies with hapten (80% saturation) causes a significant change of the quaternary structure, expressed by a decrease in the maximum diameter of about 2 nm, of the radius of gyration by 5.5%, and of the volume. The same antibodies, in which the single inter-heavy-chain disulfide bridge was opened by reduction and carboxamidomethylation, do not show any significant decrease in the overall molecular parameters upon reaction with hapten, except for a local structural change in a part of the molecule. These data lend further support to the notion that binding of hapten induces a conformational transition in its specific antibodies and suggest that the opening of the interchain disulfide bridges affects that transition. The dimensions of the intact antibodies calculated from measurements of small-angle x-ray scattering at low concentrations agree closely with those obtained from crystallographic studies.
Points of contact between histone H1 and the histone octamer.
Authors: Boulikas T , Wiseman J M , Garrard W T
Published: May 2006

The topography of the interaction between histone H1 and the histone octamer has been investigated. Bovine thymus nuclei or enzymatically fragmented chromatin were treated 1-ethyl-3(3-dimethylaminopropyl)carbodiimide, which catalyzes the formation of covalent bonds between residues of proteins in electrostatic contact. Histone H1-core histone dimers were identified and the segments of molecules participating in crosslinking were elucidated. The results demonstrate that the major histone H1-core histone dimer generated upon carbodiimide crosslinking of intact nuclei, chromatin, or mononucleosomes consists of the segment of histone H1 containing amino acids 74-106 crosslinked to the segment of histone H2A containing amino acids 58-129. Thus, the central globular region of histone H1 intimately contacts the histone octamer. Besides histone H1-H2 dimers, two other histone H1-containing crosslinked products were detected. In these instances, the segments of histone H1 molecules containing amino acids 1-72 were shown to participate in crosslinking. The histone H1 contact points defined here all occur within mononucleosomes and not between nucleosomes. These results permit the formulation of a testable model for the arrangement of histone H1 along polynucleosome chains.
Thermal stability of type I and type III procollagens from normal human fibroblasts and from a patient with osteogenesis imperfecta.
Authors: Peltonen L , Palotie A , Hayashi T , Prockop D J
Published: May 2006

Type I and type III procollagens were isolated from the medium of human fibroblast cultures in amounts adequate for examination by circular dichroism. Type I procollagen had a spectrum similar to that of type I procollagen and collagen from chicken embryos. The human type III procollagen showed a red shift not seen in type III collagen from calf skin. The midpoint (tm) for the helix-to-coil transition for both human procollagens was 40 degrees C. the same tm values were obtained with type I and type III procollagens synthesized by fibroblasts from a patient with osteogenesis imperfecta. Type I procollagen synthesized by the patient's fibroblasts, however, tended to aggregate more readily than type I procollagen from normal human fibroblasts, apparently because of a structural alteration of the protein.
Specificity of diffusion channels produced by lambda phage receptor protein of Escherichia coli.
Authors: Luckey M , Nikaido H
Published: May 2006

The lamB protein, the receptor for phage lambda, was purified from the outer membrane of Escherichia coli K-12 by extraction with Triton X-100 and EDTA, chromatography on DEAE-Sephacel in Triton X-100, exchange of Triton for cholate by gel filtration, and chromatography on Sephacryl S-200 in cholate, NaCl, and EDTA. The purified protein appeared to exist as several oligomeric species. In an equilibrium retention assay with reconstituted vesicles containing phospholipids and lipopolysaccharide, the lamB protein conferred permeability for disaccharides. In a liposome swelling assay designed to measure rates of diffusion, the lamB protein conferred permeability to phospholipid liposomes for a variety of substrates. The rates obtained indicate the permeation facilitated by the lamB protein is specific, discriminating among substrates by both size and configuration. For example, maltose diffused into liposomes 40 times faster than sucrose, about 8 times faster than cellobiose, and about 12 times faster than maltoheptaose. The results suggest that the lamB protein forms a transmembrane channel containing a site (or sites) that loosely interacts with the solutes.
Identification of blue-green algal nitrogen fixation genes by using heterologous DNA hybridization probes
Authors: Mazur Barbara J. , Rice Douglas , Haselkorn Robert
Published: May 2006

In the filamentous blue-green alga
Anabaena
7120, aerobic nitrogen fixation is linked to the differentiation of specialized cells called heterocysts. In order to study control of heterocyst development and nitrogen fixation in
Anabaena
, we have used cloned fragments of the
Klebsiella pneumoniae
nitrogen fixation (
nif
) genes as probes in DNA·DNA hybridizations with restriction endonuclease fragments of
Anabaena
DNA. Using this technique, we were able to identify and clone
Anabaena nif
genes, demonstrating the feasibility of using heterologous probes to identify genes for which no traditional genetic selection exists. From the patterns of hybridization observed, we deduced that although DNA sequence homology has been retained between some of the
nif
genes of these divergent organisms, the
nif
gene order has been rearranged.
Substituent effects on the nitrogen-15 and carbon-13 shieldings of some
N
-arylguanidinium chlorides
Authors: Botto Robert E. , Schwartz Joseph H. , Roberts John D.
Published: May 2006

The
13
C and
15
N chemical shifts of five
N
-arylguanidinium chlorides carrying polar substituents, ranging in character from 4-methoxy to 4-nitro groups, have been determined by NMR spectroscopy at the natural-abundance level of
13
C and
15
N in dimethyl sulfoxide solution. Comparison of the
13
C shifts of these salts with those of monosubstituted benzenes shows that the guanidinium group induces an average downfield shift of -5.8 ppm of the resonance of the aryl carbon to which it is attached (C1), an average upfield shift of +4.2 ppm for C2 and C6, and a small upfield shift of +1.9 ppm for C4. The shifts of C3 and C5 are small and erratic relative to the corresponding carbons in monosubstituted benzenes. The
15
N resonances of the guanidinium nitrogens are quite sensitive to electric effects resulting from substitution of polar groups at C4. The
15
N shift of the [unk]NAr nitrogen relative to that of the salts suggests that the predominant tautomer for
N
-arylguanidines is (H
2
N)
2
C[unk]NAr. The
15
N shifts of the (NH
2
)
2
nitrogens correlate rather well with σ

p

-
parameters, whereas the shifts of the -NHAr nitrogens seem to correlate only with
R
values derived from the σ

p

-
substituent constants.
Physical interaction and activity coupling between two enzymes induced by immobilization of one.
Authors: Tu S C , Hastings J W
Published: May 2006

Flavin reductase and bacterial luciferase are believed to be coupled in the in vivo light emitting reaction. In extracts, however, they are both soluble enzymes that exhibit little or no association. Immobilized luciferase, covalently attached to Sepharose, was found to bind the soluble reductase and to exhibit activity in the coupled reaction reaction with an enhanced efficiency of electron transfer.