A guanine nucleotide-sensitive adenylate cyclase in the yeast Saccharomyces cerevisiae

Adenylate cyclase in particulate extracts of Saccharomyces cerevisiae utilized either MnATP or MgATP as substrate. A mutation in the CYR1 gene, which codes for the catalytic unit of yeast adenylate cyclase (Matsumoto, K., Uno, I., and Ishikawa, T. (1983) Cell 32, 417-423), eliminated utilization of both MgATP and MnATP, indicating that a single enzyme was responsible for both activities. GTP and guanylyl-5'-imidodiphosphate stimulated yeast adenylate cyclase, while a GDP analog, guanosine-5'-O-(2-thiodiphosphate), competitively inhibited this stimulation. Thermal inactivation studies distinguished putative guanine-nucleotide regulatory protein (N) from the catalytic unit (C) of yeast adenylate cyclase. Yeast N, which conferred guanine nucleotide regulation and the ability to utilize MgATP on yeast C, was quickly inactivated by incubation of particulate extracts at 30 degrees C. In contrast, yeast C, which apparently utilized MnATP as substrate in the absence of a functional N protein, resisted inactivation at 30 degrees C. These observations suggested that physically distinct protein components mediated the catalytic activity of yeast adenylate cyclase and its regulation by guanine nucleotides. These findings indicate a striking homology between the adenylate cyclase systems of S. cerevisiae and those of vertebrate cells.