A fucose-deficient glycoprotein precursor to Rauscher leukemia virus gp69/71.

Abstract

Rauscher leukemia virus glycoprotein gp9/71 is synthesized in virus-infected cells by way of a 90,000 dalton glycoprotein precursor, termed Pr2a+b. This precursor could blaeled with radioactive glucosamine and methionine but not with fucose; whereas gp69/71 could be detected by labeling with radioactive glucosamine, fucose, or a mixture of amino acids but seemed to be deficient in methionine relative to Pr2a+b. Pr2a+b and gp69/71 were specifically precipitated by an antiserum prepared against phosphocellulose purified Rauscher gp69/71. Other virus-specific precursors, in addition to Pr2a+b, could be precipitatedby antiserum prepared against detergent disrupted virus. Neither Pr2a+b nor gp69/71 was precipitated from cell extracts by antisera to Rauscher p30. Tryptic maps of Pr2a+b and gp69]71 showed that these glycoproteins share many tryptic peptides. Pulse-chase experiments with 14C-labeled amino acids indicated that gp69/71 was not radio-labeled during the pulse-labeling period but slowly appeared during the chase incubations. Pr2a+b, however, was rapidly labeled and tended to disappear during long chases. Furthermore, two nonglycosylated viral proteins, termed pl5E and pl2E, are structurally related to Pr2a+b. Viral p15E and pl2E contained-the same methionine-containing tryptic peptide fraction as Pr2a+b as determined by ion-exchange chromatography. These results provide evidence that Pr2a+b is a precursor to gp69/71 and establish a structural and possible precursor-product relationship between Pr2a+b, pl5E, and pl2E. RNA tumor virus structural proteins are made by way of relatively large precursor polypeptides. In the avian system, p27, p19, p15, and p12 sequences are found in a 76,000 dalton precursor present in avian myeloblastosis virus-infected cells (1)*. In the murine system, Rauscher leukemia virus (RLV) p30 sequences are present in several precursors ranging in size from 65,000 to 200,000 daltons (2-4). Peptide sequences of another viral protein, termed pl5E (5)

Processing of the env Gene Products of Moloney Murine Leukaemia Virus

“…Radioactivity in gp70 appeared following 30 min of chase incubation, but did not accumulate within the infected cell to any appreciable extent. Similar findings were observed in the R-MuLV system (Naso et al, 1976). We noted that no [3H]leucine radioactivity in a band corresponding to gPr93 ~nv was observed, although [14C]tyrosineqabelled M-MuLV gpT0 was purified from fluid virus subjected to gel filtration in 6 M-guanidine-HC1 and further purified by SDS-PAGE as described in Methods.…”

“…Naso et al (1976) previously reported the presence of methionine-containing tryptic peptides of pl5(E)/pl2(E) within gPr90 ~nv for the R-MuLV system. However, no detectable R-MuL'v; gp70-specific methionine-containing tryptic peptides were found within the precursor.…”

“…Karshin et al (1977) were able to demonstrate the presence of R-MuLV gp70 and pl5(E) tyrosine tryptic peptides within R-MuLV gPr90 env. Because p 15(E) is present in only minor amounts in murine retroviruses (Naso et al, 1976;Karshin et al, 1977), we chose to digest pl2(E), a major virus protein, with trypsin. We also had difficulty in obtaining tyrosine-labelled pl2(E) from M-MuLV, but were able to label pl2(E) with [3H]leucine.…”

A Comparison of the Intracellular Precursor Polyproteins of Simian Sarcoma-associated Virus [SiSV(SiAV)] and Three Human Virus Isolates: HL23V, HEL12V and A1476V

“…The precursor proteins are apparently analogous to those seen in both the murine and avian systems (Naso et al, 1976;Karshin et al, 1977;Arcement et al, 1977;Jamjoom et al, 1977;Eisenman & Vogt, 1978;Kopchick et al, 1978). Recent reports on the endogenous primate type C viruses of baboons (BaEV) also indicate that their virus proteins are made via similar but not completely analogous precursor cleavage pathways (Whiteley & Naso, 1981).…”

Structural Differences in Envelope Glycoproteins Associated with Rat Leukaemia Virus Produced by Novikoff Hepatocellular Carcinoma and Spontaneously Transformed Wistar Rat Embryo Cells

“…When analysed by two-dimensional PAGE, both glycoproteins demonstrated a similar range of pls. Both glycoproteins also showed a similar increase in mobility when analysed by SDS-PAGE in the absence of reducing agent, suggesting that like MuLV gp70 (Naso et al, .1976;Pinter & Fleissner, 1977;Witte et al, 1977) at least some forms of Nov gp64 and WRC gp68 are present on the cell surface as disulphidelinked complexes with a protein of approximate Mr 15000. In addition, we also observed that the electrophoretic mobility of both glycoproteins increased under non-reducing conditions, resulting in Mrs of 62000 and 57000 for WRC gp68 and Nov gp64, respectively.…”