Expression of Sperm-Activating Peptide IV Receptor-Associated Membrane Guanylyl Cyclase in the Testis of the Sea Urchin Diadema setosum

Abstract

Abstract We obtained the full-length cDNA clone (DsPTGC04) encoding a membrane guanylyl cyclase expressed in the testis of the sea urchin Diadema setosum, the egg jelly of which contains sperm-activating peptide IV. The cDNA was 4305 bp long and an open reading frame predicted a protein of 1127 amino acids including an apparent signal peptide of 24 residues. The mature protein of 1103 amino acids is composed of a single transmembrane domain of 25 amino acids that divides the mature protein (Mw 123818) into an amino-terminal, extracellular domain of 484 amino acids and a carboxyl-terminal, intracellular domain of 594 amino acids, with the latter consisting of two clearly defined subdomains, a protein kinase-like and a cyclase catalytic. Four potential N-linked glycosylation sites are present in the extracellular domain and 4 presumed phosphorylatable serine residues are conserved in the cyclase catalytic domain. Northern blot analysis demonstrated that the 4.5 kb mRNA for DsPTGC04 is expressed only in the ...