A PROLINE-RICH PROTEIN, VERPROLIN, INVOLVED IN CYTOSKELETAL ORGANIZATION AND CELLULAR GROWTH IN THE YEAST SACCHAROMYCES-CEREVISIAE

A gene (VRP1) encoding a novel proline-rich protein (verprolin) has be en isolated from the yeast Saccharomyces cerevisiae as a result of its hybridization to a chick vinculin cDNA probe. The deduced protein seq uence contains 24% proline residues present as proline-rich motifs thr oughout the verprolin sequence. Several of these motifs resemble recen tly identified sequences shown to bind Src homology 3 (SH3) domains in vitro. Replacement of the wild-type VRP1 allele with a mutant allele results in strains that grow slower than wild-type strains and are tem perature sensitive. The vrp1 mutants are impaired in both cell shape a nd size and display aberrant chitin and actin localization. We propose that verprolin is involved in the maintenance of the yeast actin cyto skeleton, through interactions with other proteins, possibly containin g SH3 domains.