Identification of the domain of Saccharomyces cerevisiae adenylate cyclase associated with the regulatory function of RAS products

Abstract

Various truncated CYR1 genes of Saccharomyces cerevisiae were fused to efficient promoters and expressed in Escherichia coli and S. cerevisiae cells with or without the RAS genes. The catalytic domain of adenylate cyclase encoded by the 3'-terminal 1.3 kb region of the open reading frame of the CYR1 gene produced cyclic AMP, irrespective of the presence of RAS genes. The product of the 3'-terminal 2.1 kb region of CYR1 showed guanine nucleotide-dependent adenylate cyclase activity and produced a large amount of cAMP in the presence of the RAS gene. Thus, the domain encoded by the 0.8 kb region adjacent to the catalytic domain is associated with the regulatory function of the RAS products. The cyr1 RAS1 RAS2 cells carrying the 3'-terminal 1.3 kb region of CYR1 were unable to respond to environmental signals such as sulfur starvation and temperature shift, but the cyr1 cells carrying the 2.1 kb region and at least one RAS gene were able to respond to these signals. The environmental signals may be transferred to the adenylate cyclase system through the RAS products.