Arenavirus Stable Signal Peptide Is the Keystone Subunit for Glycoprotein Complex Organization

Bederka, Lydia H.; Bonhomme, Cyrille J.; Ling, Emily L.; Buchmeier, Michael J.

Mutations within the FLLL motif affect glycoprotein fusion activity. In order to assess if the FLLL GPC mutants produced a functional glycoprotein complex, we performed a pH-dependent fusion assay (29, 40) . Transfected DBT cells were subjected to acidic growth medium to induce syncytium formation via conformational changes within the glycoprotein (41) . The mutants that allowed for GP2 detection, FALA GPC and YALL GPC, produced various levels of fusion activity. FALA GPC resulted in one-third the fusion activity of that of the wild-type glycoprotein. YALL GPC allowed for roughly half the level of fusion activity compared to that of the wild-type GPC (Fig. 5) . Coexpression of the wildtype SSP resulted in a decrease in fusion activity for both FALA GPC and YALL GPC, whereas cotransfection slightly increased ALLA GPC fusion activity, although this amount was not appreciably higher than background levels.