Molecular cloning and sequence analysis of feline gastrin cDNA

Abstract

An oligo (dT)-primed cDNA coding for the gastrin precursor was constructed from poly(A)-containing RNA isolated from feline antral mucous cells. The cDNA was inserted into the EcoRI endonuclease site of lambda gt10 vector. Clones containing gastrin sequence were selected by hybridization to a single-stranded 32p-labeled DNA probe synthesized from the porcine gastrin cDNA by primer extension method. The nucleotide sequence of the cDNA insert (475 nucleotides) revealed 325 nucleotids in the entire mRNA coding region, 46 nucleotides in the 5``-untranslated region, 96 nucleotides in the 3``-untranslated region, and a poly(A) tail of 18 nucleotides. Gastrin is located near the carboxyl end of preprogastrin. A considerable nucleotide sequence homology between the coding region of feline preprogastrin and that of other mammalian species has been found; the feline sequence shows 83\% homology with porcine sequence, 86\% with human, 80\% with rat, and 91\% with canine sequence. There always have been three dibasic amino acids in other mammalian preprogastrin published previously. Surprisingly, the first dibasic amino acid, Arg-Arg (57-58 residues), is replaced with Arg-Trp though the other two dibasic amino acids exists. The 14 nucleotide sequence following polyadenylational signal (AAUAAA) is very highly conserved (84\%) among mammalian gastrin cDNA.