Genomic structure and expression of the sea urchin soluble guanylyl cyclase β subunit gene

We obtained the full-length cDNA and genomic DNA clones of HpGCS-beta (1) encoding the beta subunit of soluble guanylyl cyclase (soluble GC), which is expressed in the testis and ovary of the sea urchin Hemicentrotus pulcherrimus. Reverse transcription-polymerase chain reaction analysis demonstrated that the HpGCS-beta (1) transcript was detected in unfertilized eggs as well as in the testis and ovary. The open reading frame predicted a protein of 604 amino acids with a putative cyclase catalytic domain conserved in membrane GCs and adenylyl cyclases. (105)His, (78)Cys, and (122)Cys, important amino acids for heme-binding in the beta (1) subunit of soluble GCs in vertebrates, were conserved in the corresponding positions of HpGCS-beta (1). The HpGCS-beta (1) gene consisted of 8 exons and had a span of 26 kbp. A comparison of genomic structure of the HpGCS-beta (1) gene with that of the soluble GC beta (1) subunit gene (OIGCS-beta (1)) of the medaka fish indicated that exon 4 in the HpGCS-beta (1) gene corresponds to exons 4 to 9 in the OIGCS-beta (1) gene.