Role of signal recognition particle in the membrane assembly of Sindbis viral glycoproteins

Abstract

The role of signal recognition particle (SRP) in the biosynthesis of Sindbis glycoproteins was investigated by translating the viral 26S mRNA in a wheat-germ cell-free system. SRP has no effect on the synthesis or proteolytic processing of the cytoplasmic C protein. The membrane integration and the proteolytic processing of the viral glycoproteins PE2 and E1 were demonstrated to be SRP-dependent. In the absence of microsomal membranes, SRP caused an arrest of the synthesis of the viral glycoproteins. This arrest could be released by the addition of salt-extracted microsomal membranes. Synchronization experiments indicated that the uncleaved signal sequence of PE2 was recognized by SRP after at most 130 amino acids of PE2 were polymerized. No apparent interaction of SRP with a putative signal sequence of E1 and/or a 6 kilodalton peptide could be detected.