Sequence of a cDNA encoding pancreatic preprosomatostatin-22.

Abstract

The nucleotide sequence of a precursor to somatostatin that upon proteolytic processing may give rise to a hormone of 22 amino acids is reported. The nucleotide sequence of a c[complementary]DNA from the channel catfish (Ictalurus punctatus) encodes a precursor to somatostatin that is 105 amino acids (MW 11,500). The cDNA coding for somatostatin-22 consists of 36 nucleotides in the 5'' untranslated region, 315 nucleotides that code for the precursor to somatostatin-22, 269 nucleotides at the 3'' untranslated region, and a variable length of poly(A). The putative preprohormone contains a sequence of hydrophobic amino acids at the amino terminus that has the properties of a signal peptide. A connecting sequence of .apprx. 57 amino acids is followed by a single Arg-Arg sequence, which immediately precedes the hormone. Somatostatin-22 is homologous to somatostatin-14 in 7 of the 14 amino acids, including the Phe-Trp-Lys sequence. Hybridization selection of mRNA, followed by its translation in a wheat germ cell-free system, resulted in the synthesis of a single polypeptide having a MW of .apprx. 10,000 as estimated on NaDodSO4/polyacrylamide gels.