Molecular cloning and expression of prohormone convertases PC1 and PC2 in the pituitary gland of the bullfrog, Rana catesbeiana

Abstract

We cloned cDNAs encoding PC1 and PC2 from a cDNA library constructed for the anterior pituitary gland of the bullfrog (Rana catesbeiana) and sequenced them. The bullfrog PC1 cDNA consisted of 2972 base pairs (bp) with an open reading frame of 2208 bp and encoded a protein of 736 amino acids, including a putative signal peptide of 26 amino acids. The protein showed a high homology to R. ridibunda PC1 (95.1%) and mammalian PC1 (72.6%). The bullfrog PC2 cDNA consisted of 2242 bp with an open reading frame of 1914 bp and encoded a protein of 638 amino acids, including a putative signal peptide of 23 amino acids. This protein showed a high homology to R. ridibunda PC2 (95.5%) and mammalian PC2 (84.8%). The catalytic triad of serine proteinases of the subtilisin family was found at Asp-168, His-209, and Ser-383 in the PC1 protein and at Asp-167, His-208, and Ser-384 in the PC2 protein. In situ hybridization staining revealed that PC2 mRNA was detected in corticotrope cells of the tadpoles, but not in those of the adults. In the adult, only PC1 mRNA was detected in the pars distalis but both PC1 and PC2 mRNAs were detected in the pars intermedia. The data also showed that PC1 mRNA was expressed in gonadotrope cells.