Functional analysis of late-budding domain activity associated with the PSAP motif within the vesicular stomatitis virus M protein

A PPPY motif within the M protein of vesicular stomatitis virus (VSV) functions as a late-budding domain (L-domain); however, L-domain activity has yet to be associated with a downstream PSAP motif. VSV recombinants with mutations in the PPPY and/or PSAP motif were recovered by reverse genetics and examined for growth kinetics, plaque size, and budding efficiency by electron microscopy. Results indicate that unlike the PPPY motif, the PSAP motif alone does not possess L-domain activity. Finally, the insertion of the human immunodeficiency virus type 1 p6 L-domain and flanking sequences into the PSAP region of M protein rescued budding of a PPPY mutant of VSV to wild-type levels.