Role of partial proteolysis in processing murine leukemia virus membrane envelope glycoproteins to the cell surface. A viral mutant with uncleaved glycoprotein

C. A. Machida, D. Kabat

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We have isolated a mutant Rauscher murine leukemia virus (R-MuLV) with a mutation in its envelope (env) glycoprotein gene. This mutant encodes a membrane glycoprotein with an apparent M(r)= 80,000 (gPr80(env)) that contains both gp70 and p15E antigenic determinants found in the larger wild type R-MuLV env precursor molecule gPr90(env). Glycosylation inhibition and peptide mapping analyses indicate that the smaller size of the mutant glycoprotein is caused by a shortening of its polypeptide chain rather than by reduced glycosylation. Unlike gPr90(env) of wild type R-MuLV which contains Asn-linked high mannose oligosaccharides and is processed by partial proteolysis and by further glycosylation in the Golgi apparatus to produce gp70 plus g15E, the mutant glycoprotein can reach the cell surface without proteolysis. The uncleaved plasma membrane component, which undergoes further glycosylation during its transit through the Golgi apparatus, has an apparent M(r)= 85,000. Furthermore, this cell surface glycoprotein is incorporated into released virions which are infectious. However, the mutant envelope glycoproteins on the cell surface do not block the receptors needed for superinfection by wild type MuLV. These results indicate that transport of uncleaved env gene-encoded glycoproteins to the cell surface is not a unique attribute of leukemia-producing recombinant or dual tropic MuLVs, but can also occur with a mutant of ecotropic MuLV.

Original languageEnglish (US)
Pages (from-to)14018-14022
Number of pages5
JournalJournal of Biological Chemistry
Issue number23
StatePublished - Dec 1 1982


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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