Mutant regulatory subunit of 3′,5′-cAMP-dependent protein kinase of yeast Saccharomyces cerevisiae

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Abstract
Four mutants with amino acid substitution(s) at or near the putative phosphorylation site (Arg142 Arg143 Thr144 Ser145) of the regulatory subunit of cAMP-dependent protein kinase were obtained by site-directed mutagenesis. Three mutants, BCY1 Ala 145 (Ser145 to Ala), BCY1 His 143 (Arg143 to His) and BCY1 Asn 144, Ala 145 (Thr144 to Asn and Ser145 to Ala) complemented a bcy1 mutant, whereas BCY1 Gly 143 (Arg143 to Gly) did not. In addition, mutant, BCY1 Asn 144, Ala 145 exhibited a dominant coldsensitive phenotype, which can be most easily explained by the functional alteration of the regulatory subunit of cAMP-dependent protein kinase by the mutations. Analyses of these mutant genes revealed that phosphorylation of the regulatory subunit is not a prerequisite for the regulation of the cAMP-dependent protein kinase activity in responding to the cAMP level.