Glycopeptides of Murine Leukemia Viruses I. Comparison of Two Ecotropic Viruses

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Abstract
The glycopeptides obtained by Pronase digestion of 2 ecotropic stains of murine leukemia virus (MuLV) were compared by gel filtration. Four different glycopeptide size classes, designated G1, G2, G3 and G4, with MW of approximately 5100, 2900, 1500, respectively, were associated with Rauscher MuLV virions grown in [mouse bone marrow] JLS-V9 cells. Various sugar precursors, including glucosamine, galactose, fucose and mannose, were incorporated into G1 and G2, suggesting that these are complex (type I) glycopeptides. The 2 smaller glycopeptide size classes, G3 and G4, were mannose-rich (type II) glycopeptides. G4 was more sensitive to digestion with endo-.beta.-N-acetylglucosaminidase H than G3, suggesting that the core of G3 may contain fewer mannose residues. Glycopeptides of the same size class as G1 and G2 were associated with Rauscher MuLV and AKR-MuLV grown in III6A (mouse embryo) cells. Previous studies showed that gp52, a proteolytic cleavage product of gp70, possessed primarily G1 glycopeptides and that gp52 was more highly sulfated than gp70. G1 is approximately 2-fold more highly sulfated than G2, explaining the observed difference in sulfation of gp52. The unusually large size of G1 suggested that infection with MuLV may alter the host cell glycosylation pattern. To test this possibility, glycopeptides from Sindbis virions grown in uninfected and Rauscher MuLV-infected JLS-V9 cells were compared, and no differences were observed. G1 was not detected in Sindbis virions, indicating that acquisition of G1 depends on properties of the virus-coded polypeptide backbone of the gp70 molecule.