ACTIN CYTOSKELETON AND BUDDING PATTERN ARE ALTERED IN THE YEAST RVS161 MUTANT - THE RVS161 PROTEIN SHARES COMMON DOMAINS WITH THE BRAIN PROTEIN AMPHIPHYSIN

The actin cytoskeleton cells is altered in rvs161 mutant yeast, with t he defect becoming more pronounced under unfavorable growth conditions , as described for the rvs167 mutant. The cytoskeletal alteration has no apparent effect on invertase secretion and polarized growth. Mutati ons in RVS161, just as in RVS167, lead to a random budding pattern in a/alpha diploid cells. This behavior is not observed in a/a diploid ce lls homozygous for the rvs161-1 or rvs167-1 mutations. In addition, se quence comparisons revealed that amphiphysin, a protein first found in synaptic vesicles of chicken and shown to be the autoantigen of Stiff Man syndrome, presents similarity with both Rvs proteins. Furthermore , limited similarities with myosin heavy chain and tropomyosin alpha c hain from higher eukaryotic cells allow for the definition of a possib le consensus sequence. The finding of related sequences suggests the e xistence of a function for these proteins that is conserved among euka ryotic organisms.