Synechocystis Strain PCC 6803 cya2, a Prokaryotic Gene That Encodes a Guanylyl Cyclase

Synechocystis strain PCC 6803 exhibits similar levels of cyclic AMP (cAMP) and cyclic GMP (cGMP). A thorough analysis of its genome showed that Cya2 (Sll0646) has all the sequence determinants required in terms of activity and purine specificity for being a guanylyl cyclase. Insertional mutagenesis of cya2 caused a marked reduction in cGMP content without altering the cAMP content. Thus, Cya2 represents the first example of a prokaryotic guanylyl cyclase.