Yeast cAMP-dependent protein kinase regulatory subunit mutations display a variety of phenotypes

Abstract

Ten spontaneous and four in vitro constructed mutations in the gene encoding the regulatory subunit of cAMP-dependent protein kinase of Saccharomyces cerevisiae display very different phenotypes. The DNA nucleotide sequence of each spontaneous mutation was determined. Mutations were found in both the cAMP-binding domains and proximal to the cAMP-dependent protein kinase phosphorylation site. The latter mutations exhibited dominant traits when gene dosage was increased. The variation of phenotypes of sra1 mutations was examined. Many aspects of growth are affected, including growth on nonfermentable carbon sources, accumulation of glycogen, ability to sporulate, and ability to survive starvation. The null mutations affect all these traits. None of the spontaneous mutations confer the null phenotype. Instead, these mutations can be placed into groups of increasing severity based on the number of traits affected. These traits reflect the functions of the cAMP-dependent protein kinase substrates and ranking of sra1 phenotypes probably reflects a progressive defect in one or more aspects of the regulatory subunit function.