On the hsp26 of Saccharomyces cerevisiae.

The function of the small size hsps in Saccharomyces cerevisiae has yet to be convincingly established. In this paper we present some aspects of the physiology of hsp26. Several mutant strains were analyzed with respect to the expression of the HSP26 gene using anti-hsp26 antibody for identification. The bcy1 mutant which lacks the regulating subunit of protein kinase A failed to produce full expression of HSP26 under heat shock whereas a ras2 mutation which lowers significantly the level of cAMP, produced no detectable effect. During normal growth hsp26 protein is induced during diauxie and its synthesis continues during the second exponential phase. Both BCY1 and CYR1 genes seen to be required for induction during the transition phase albeit not directly but rather interacting with some other regulatory component. The structure of hsp26 is discussed by homology with other small hsps.