Cdc35 Background Information The guanine nucleotide exchange factor Cdc25 (also designated Ctn1) regulates adenylyl cyclase via the small G proteins Ras1 and Ras2 (also known as Glc5 or Ctn5) (1,2). The yeast RAS proteins regulate cell growth and development by cycling between an active GTP-bound state and an inactive GDP-bound state (3). Adenylyl cyclase, encoded by the Cdc35 gene (also designated Cyr1, Hrs1 or Sra4), catalyzes the formation of the second messenger cAMP (4,5). cAMP exerts its effects via a cAMP-dependent kinase consisting of two regulatory subunits, encoded by Bcy1 (also designated Reg1 or Sra1), and two catalytic subunits, encoded by Tpk1 (also designated Pka1 or Sra3) (6,7).
