Yeast mating pheromone alpha factor inhibits adenylate cyclase.

The pheromone alpha factor, secreted by Saccharomyces cerevisiae cells of the alpha mating type, serves to synchronize the opposite mating type (a cells) at G1 as a prelude to fusion of the two cell types. We found that, in vitro, alpha factor inhibited the membrane-bound adenylate cyclase of these cells in a dose-dependent manner. Moreover, one class (ste5) of a cell mutants that grow normally at either 23 degrees or 34 degrees C but that are unable to respond to alpha factor or to mate at the higher temperature possessed an adenylate cyclase activity that was not inhibited by alpha factor at 34 degrees C but was fully sensitive to inhibition at 23 degrees C. Furthermore, addition of cyclic AMP to a cell culture medium shortened the period of pheromone-induced G1 arrest. We conclude that inhibition of adenylate cyclase activity by alpha factor may constitute, at least in part, the biochemical mode of action of the pheromone in vivo.