Fatty acid binding to vesicular stomatitis virus glycoprotein: a new type of post-translational modification of the viral glycoprotein

The glycoprotein (G) of vesicular stomatitis virus (VSV) binds 1–2 moles of fatty acid per mole of protein. The fatty acids cannot be released by repeated extractions of the protein with organic solvents, nor can they be released by denaturing the protein with ionic or nonionic detergents. Pronase digestion of G yields an organic extractable fragment that contains bound fatty acid. The fatty acid is quantitatively released from this fragment and from intact G by mild alkali treatment in methanol and is identified by gas-liquid and thin-layer chromatography as, predominantly, the methyl ester of palmitic acid. Insignificant amounts of phosphate are found in G, thus ruling out the presence of bound phospholipid. Chicken embryo fibroblast pre-labeled with 3H-palmitate and then infected with VSV for 4 hr show the presence of 3H label in G but not in other viral structural proteins. The 3H label is present only in the fatty acid moiety of the protein. Much smaller amounts of 3H fatty acid are bound to G protein formed by the VSV mutant ts045 grown at the nonpermissive temperature, and no 3H fatty acid is bound to G synthesized at 37°C in cells pretreated with tunicamycin, an inhibitor of glycosylation. However, infection with the VSV-Orsay strain at 30°C in the presence of tunicamycin allows for production of VSV particles with nonglycosylated G ( Gibson et al., 1979 Gibson R. Schlesinger S. Kornfeld S. The nonglycosylated glycoprotein of vesicular stomatitis virus is temperature sensitive and undergoes intracellular aggregation at elevated temperatures. J. Biol. Chem. 1979; 254: 3600-3607 Abstract Full Text PDF Google Scholar ), and this G has the same proportion of the fatty acid as does the normal glycosylated G. These data indicate that fatty acids become covalently attached to the G polypeptide chain during maturation of the protein—perhaps as the glycoprotein moves to the cell's plasma membrane.