xP1 and xP4. P-domain peptides expressed in Xenopus laevis stomach mucosa

Two different precursors for secretory polypeptides from the stomach of Xenopus laevis have been characterized by cDNA cloning. Both mature polypeptides are potential candidates for gastrointestinal growth factors. One, xP1, is the X. laevis homologue of the pS2 gene product consisting only of a single P-domain, whereas the second, xP4, is a novel polypeptide formed by four P-domains arranged in tandem. Northern analysis detected both transcripts in the stomach but not in the skin or the brain. In situ hybridizations localized the expression of both precursors in surface mucous cells of the gastric mucosa. With an antibody generated against the deduced C-terminal end of xP4, the mature polypeptide was investigated by Western analysis revealing N-glycosylation of xP4.