The Dictyostelium homologue of mammalian soluble adenylyl cyclase encodes a guanylyl cyclase

A new Dictyostelium discoideum cyclase gene was identified that encodes a p rotein (sGC) with 35% similarity to mammalian soluble adenylyl cyclase (sAC ). Gene disruption of sGC has no effect on adenylyl cyclase activity and re sults in a > 10-fold reduction in guanylyl cyclase activity. The scg- null mutants show reduced chemotactic sensitivity and aggregate poorly under str ingent conditions. With Mn2+/GTP as substrate, most of the sGC activity is soluble, but with the more physiological Mg2+/GTP the activity is detected in membranes and stimulated by GTP gammaS. Unexpectedly, orthologues of sGC and sAC are present in bacteria and vertebrates, but absent from Drosophil a melanogaster, Caenorhabditis elegans, Arabidopsis thaliana and Saccharomy ces cerevisiae.