Intracellular appearance of a glycoprotein in VSV-infected BHK cells lacking the membrane-anchoring oligopeptide of the viral G-protein.

Infection of BHK 21 cells by vesicular stomatitis virus (VSV) results in the intracellular synthesis of the five viral proteins which are easily detectable in polyacrylamide gels after short labeling periods with [35S]methionine. In addition, a 6th prominent radioactive protein band appears intracellularly in VSV-infected BHK cells. This additional polypeptide is also coded by the viral genome, because it is immunoprecipitated by antibodies against viral particles and more specifically by antibodies against purified G-protein. We propose to call this derivative of the G-protein Gsi-protein (short intracellular G-protein). It is associated with intracellular membranes and has an apparent mol. wt. of 58 000. Both G- and Gsi-protein have the same kinetics of appearance in the cell. The ratio of G-:Gsi-protein in BHK 21 cells is approximately 85:15. The mol. wt. difference of approximately 6000 daltons between G- and Gsi-protein is not due to variations in the degree of glycosylation because trypsin digestions of both [3H]mannose-labeled glycoproteins gave rise to identical glycopeptide patterns. Incubation of microsomes with trypsin demonstrates that Gsi-protein is protected in its full length by intracellular membranes. Gsi-protein is lacking an extended carboxy-terminal region of the viral G-protein sequence because it is not modified by palmitic acid and is not immunprecipitated by specific antibodies against a C-terminal peptide of the G-protein. Limited proteolysis by endoproteinase arg C indicates that the structure of Gsi-protein is very similar to the shedded form of the G-protein which has been previously described in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)