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

Abstract
A new Dictyostelium discoideum cyclase gene was identified that encodes a protein (sGC) with 35% similarity to mammalian soluble adenylyl cyclase (sAC). Gene disruption of sGC has no effect on adenylyl cyclase activity and results in a >10‐fold reduction in guanylyl cyclase activity. The scg − null mutants show reduced chemotactic sensitivity and aggregate poorly under stringent conditions. With Mn2+/GTP as substrate, most of the sGC activity is soluble, but with the more physiological Mg2+/GTP the activity is de tected in membranes and stimulated by GTPγS. Unexpectedly, orthologues of sGC and sAC are present in bacteria and vertebrates, but absent from Drosophila melanogaster , Caenorhabditis elegans , Arabidopsis thaliana and Saccharomyces cerevisiae .