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Glycopeptides of murine leukemia viruses. I. Comparison of two ecotropic viruses
Abstract:
The glycopeptides obtained by pronase digestion of two ecotropic strains of murine leukemia virus (MuLV) were compared by gel filtration. Four different glycopeptide size classes, designated G(1), G(2), G(3), and G(4), with molecular weights of approximately 5,100, 2,900, 2,200, and 1,500, respectively, were shown to be associated with Rauscher MuLV virions grown in JLS-V9 cells. Various sugar precursors, including glucosamine, galactose, fucose, and mannose were incorporated into G(1) and G(2), suggesting that these are complex (type I) glycopeptides. The two smaller glycopeptide size classes, G(3) and G(4), were shown to be mannoserich (type II) glycopeptides. G(4) was more sensitive to digestion with endo-beta-N-acetylglucosaminidase H than G(3), suggesting that the core of G(3) may contain fewer mannose residues. Glycopeptides of the same size class as G(1) and G(2) were associated with both Rauscher MuLV and AKR-MuLV grown in III6A (mouse embryo) cells. Previous studies have shown that gp52, a proteolytic cleavage product of gp70, possessed primarily G(1) glycopeptides and that gp52 was more highly sulfated than gp70. We observed that G(1) is approximately twofold more highly sulfated than G(2), explaining the observed difference in sulfation of gp52. The unusually large size of G(1) 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. G(1) was not detected in Sindbis virions, indicating that acquisition of G(1) depends on properties of the virus-coded polypeptide backbone of the gp70 molecule.
Insights
Murine leukemia virus (MuLV) glycopeptides were analyzed, revealing distinct size classes and glycosylation patterns. The large G(1) glycopeptide suggests MuLV infection may alter host cell glycosylation, but this is virus-specific.
Area of Science:
- Virology
- Glycobiology
- Molecular Biology
Background:
- Murine leukemia virus (MuLV) is a retrovirus known to cause various diseases in mice.
- Glycopeptides are proteins with attached carbohydrate chains, crucial for viral structure and function.
- Understanding viral glycopeptide composition is key to deciphering viral pathogenesis and developing interventions.
Purpose of the Study:
- To characterize and compare glycopeptides from different MuLV strains.
- To investigate the glycosylation patterns of MuLV-associated glycopeptides.
- To determine if MuLV infection alters host cell glycosylation.
Main Methods:
- Pronase digestion of MuLV virions.
- Gel filtration chromatography to separate glycopeptides by size.
- Analysis of sugar precursor incorporation.
- Enzymatic digestion with endo-beta-N-acetylglucosaminidase H.
- Comparison of glycopeptides from MuLV-infected and uninfected cells.
Main Results:
- Four glycopeptide size classes (G(1)-G(4)) were identified in Rauscher MuLV virions.
- G(1) and G(2) are complex (type I) glycopeptides, while G(3) and G(4) are mannose-rich (type II).
- G(1) glycopeptides are significantly more sulfated than G(2), explaining differences in gp52 and gp70 sulfation.
- No alterations in Sindbis virus glycopeptides were observed in MuLV-infected cells, indicating G(1) acquisition is virus-specific.
Conclusions:
- MuLV glycopeptide composition varies by size and type.
- The large size and high sulfation of G(1) suggest a unique role in MuLV structure or function.
- The acquisition of specific glycopeptides like G(1) is dependent on the virus-coded polypeptide backbone, not host cell alterations.