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S Oroszlan

Publications and source records attributed to S Oroszlan.

At least 19 recordsLinked to original sources
PubMed1979

Amino acid sequence homology between histone H5 and murine leukemia virus phosphoprotein p12.

The amino terminal acid sequences of several mouse leukemia virus phosphoproteins (p12) show definite homology with the amino terminal conserved region of H5 histones, the phosphorylated nuclear proteins of nucleated erythrocytes. Differences in the amino acid compositions of the two groups of proteins seem to rule out the possibility that they evolved from a single common ancestral gene. The finding of sequence homology between viral p12's and cellular histones, however, is consistent with evolution of retrovirus structural proteins by a process of differentiation from preexisting cellular genes. The conserved primary and secondary structure at the amino terminal region, common to both groups of proteins, may be related to their common function of nucleic acid binding modulated by phosphorylation.

Amino Acid Sequence↗
PubMed1979

Amino-terminal sequence of bovine leukemia virus major internal protein: homology with mammalian type C virus p30 structural proteins.

The amino acid composition, the COOH-terminal amino acid, and the NH2-terminal amino acid sequence of the first 55 residues of the major internal structural protein, p24, of bovine leukemia virus (BLV) were determined. The compositional data and the results of end-group analysis revealed that, although BLV p24 is chemically distinct, it more closely resembles the p30 structural proteins than the other gag gene products of mammalian retroviruses. It was found that BLV p24 shares the common NH2-terminal proline and COOH-terminal leucine but lacks the common prolylleucylarginine tripeptide and the larger conserved region found near the NH2 terminus of all mammalian type C viral p30s. Alignment of the amino acid sequence of BLV p24 with the previously determined sequence of feline leukemia virus p27 revealed a statistically significant sequence homology. A more distant relationship was found between BLV p24 and other mammalian p30s. The finding of a definite sequence homology between BLV p24 and mammalian type C virus p30s clearly establishes the origin of these contemporary viral proteins from common progenitor genes.

Amino Acid Sequence↗
PubMed1979

Reticuloendotheliosis virus: detection of immunological relationship to mammalian type C retroviruses.

Reticuloendotheliosis virus (REV) p30 shares cross-reactive determinants and a common NH2-terminal tripeptide with mammalian type C viral p30's. An interspecies competition radioimmunoassay was developed, using iodinated REV p30 and a broadly reactive antiserum to mammalian virus p30's. The avian leukosis-sarcoma viruses and mammalian non-type C retroviruses did not compete in this assay. Previous data indicating that the REV group is not represented completely in normal avian cell DNA lead us to speculate that this may be the first example of interclass transmission, albeit in the remote past, among the Retroviridae.

Animals↗
PubMed1979

Post-translational modification of Rauscher leukemia virus precursor polyproteins encoded by the gag gene.

Post-translational modifications of retrovirus gag gene-encoded polyproteins include proteolytic cleavage, phosphorylation, and glycosylation. To study the sequence of these events, we labeled JLS-V9 cells chronically infected with Rauscher murine leukemia virus in pulse-chase experiments with the radioactive precursors [35S]methionine, [14C]mannose, [3H]glucosamine, and [32P]phosphate. Newly synthesized gag polyproteins which incorporated label, and the modified products derived from them, were identified by immunoprecipitation of cell lysates with anti-p30 rabbit serum, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Pulse-chase experiments were carried out in the presence as well as in the absence of tunicamycin, an inhibitor of glycosylation. Among the three major polyproteins synthesized in the absence of tunicamycin, two were found to be glycosylated but not phosphorylated. These were designated gPr80gag and gP94gag. Both shared identical [35S]methionine peptides with Pr65gag and p30. Of the two nonglycosylated precursors, Pr65gag and Pr75gag, only Pr65gag was found to be detectably phosphorylated, and Pr75gag could be readily identified only when glycosylation was inhibited. On the basis of these results, a scheme for the post-translational modification of gag polyproteins is proposed. According to this scheme the gag gene-encoded polyproteins are processed from a common precursor, Pr75gag, by two divergent pathways: one leading through the intermediate Pr65gag to internal virion components via cleavage and phosphorylation and the other via tunicamycin-sensitive mannosylation to the intermediate gPr80gag, which is further glycosylated to yield cell surface polyprotein gP94gag.

Genes, Viral↗
PubMed1978

Amino- and carboxyl-terminal amino acid sequences of proteins coded by gag gene of murine leukemia virus.

The amino- and carboxyl-terminal amino acid sequences of proteins (p10, p12, p15, and p30) coded by the gag gene of Rauscher and AKR murine leukemia viruses were determined. Among these proteins, p15 from both viruses appears to have a blocked amino end. Proline was found to be the common NH(2) terminus of both p30s and both p12s, and alanine of both p10s. The amino-terminal sequences of p30s are identical, as are those of p10s, while the p12 sequences are clearly distinctive but also show substantial homology. The carboxyl-terminal amino acids of both viral p30s and p12s are leucine and phenylalanine, respectively. Rauscher leukemia virus p15 has tyrosine as the carboxyl terminus while AKR virus p15 has phenylalanine in this position. The compositional and sequence data provide definite chemical criteria for the identification of analogous gag gene products and for the comparison of viral proteins isolated in different laboratories. On the basis of amino acid sequences and the previously proposed H-p15-p12-p30-p10-COOH peptide sequence in the precursor polyprotein, a model for cleavage sites involved in the post-translational processing of the precursor coded for by the gag gene is proposed.

AKR murine leukemia virus↗
PubMed1977

Solubilized TSTA and the major viral structural proteins, gp70 and p30, in the immune response to murine leukemias induced by Friend and Rauscher virus.

Antigens present in gp70 and p30 purified from Rauscher virus, were tested for immunogenicity in various assays measuring the anti-tumor immune response against lymphocytic leukemias of Friend (FBL-3) or Rauscher (RBL-5) virus origin. p30 had no effect on in vitro cytotoxicity against tumor cell targets mediated by either an anti RBL-5 serum or lymphocytes from animals immunized with FBL-3 cells. gp70 had had no effect on serum-mediated cytotoxicity but used at high concentrations it inhibited cell-mediated cytotoxicity. When used to immunize mice directly against subsequent challenge with the RBL-5 and FBL-3 leukemias, p30 had no discernible effect, while gp70 afforded partial protection against RBL-5 but only at high concentrations. Cell-free preparations of tumor membranes containing negligible amounts of gp70 were antigenically superior to gp70 in both the in vitro and in vivo assays. It is concluded that antigens on these purified proteins that are also expressed on tumor cells are not major targets of the anti-tumor immune response in this system.

Animals↗
PubMed1977

Envelope glycoproteins of Rauscher murine leukemia virus: isolation and chemical characterization.

The envelope glycoproteins (designated gp70 and gp45) of the Rauscher strain of murine leukemia virus were solubilized by osmotic shock and freeze-thawing in chaotropic solutions. The viral glycoproteins were then purified by phosphocellulose chromatography and gel permeation chromatography on Bio-Gel A-1.5m. Yields by this procedure were 6.2% for gp70 and 1.3% for gp45 on a protein input basis. The apparent molecular weights were respectively 67 500 and 47 500 with a polypeptide chain molecular weight of approximately 45 000 for both glycoproteins. Amino acid analysis showed a high degree of similarity for both components, with some differences subject to further evaluation. The total carbohydrate content was approximately 32% for gp70 and 6-9% for gp45. In keeping with the amino acid compositional similarity suggesting relationships, alanine was found to ba the amino-terminal amino acid of both glycoproteins, and cross-reactivity was demonstrated by immunologic tests. The data suggest that the chief difference between gp70 and gp45 lies in the carbohydrate content.

Amino Acids↗