SSC1, a member of the 70-kDa heat shock protein multigene family of Saccharomyces cerevisiae, is essential for growth.

The genome of the yeast Saccharomyces cerevisiae contains a family of genes related to the HSP70 genes (encoding the 70-kDa heat shock protein) of other eukaryotes. Mutations in two of these yeast genes (SSC1 and SSD1), whose expression is increased a few fold after temperature upshift, were constructed in vitro and substituted into the yeast genome in place of the wild-type alleles. No phenotypic effects of the mutation in SSD1 were detected. However, a functional SSC1 gene is essential for vegetative growth. This result, in conjunction with experiments involving mutations in other members of this multigene family, indicates that at least three distinct functions are carried out by genes of the HSP70 family.