MUTATIONS IN A CARBOXY-TERMINAL REGION OF VESICULAR STOMATITIS-VIRUS GLYCOPROTEIN-G THAT AFFECT MEMBRANE-FUSION ACTIVITY

The envelope glycoprotein G of vesicular stomatitis virus induces memb rane fusion at acidic pH. A highly conserved amino terminal region spa nning residues 123 to 137 has previously been identified as an interna l fusion domain. Here we have substituted specific amino acids within a carboxy terminal region, conserved in five vesiculoviruses encompass ing residues 395 to 418, and studied the effect of these mutations on membrane fusion at acid pH and pH-dependent conformational change. Sub stitution of conserved Gly 395, Gly 404, Gly 406, Asp 409, and Asp 411 with Glu, Ala, Ala, Asn, and Asn, respectively, decreased the cell-ce ll fusion efficiency, as well as reduced the pH threshold of membrane fusion. Mutation of Gly 404 and Asp 409 to Lys and Ala, respectively, abolished the fusion activity. Mutant Gly 404 Lys also showed markedly altered resistance to trypsin digestion at acidic pH. These results s uggest that the region between amino acids 395 to 418 is important for the fusogenic activity of the G protein. The possible role of this do main in conformational changes involved in fusion activity of VSV G is also discussed. (C) 1998 Academic Press.