ISOLATION AND PARTIAL AMINO ACID SEQUENCE OF A 78 KDA PORCINE GASTRIN-BINDING PROTEIN

Abstract 1. 1. A 78 kDa protein (p78) has been partially purified from washed membranes isolated from the corpus of porcine gastric mucosa. The purification was monitored by covalent cross-linking of iodinated [Nle 15 ]-gastrin; 17. 2. 2. A single N-terminal sequence extending for 33 amino acids was obtained from the p78 preparation. Partial sequences totalling 192 amino acids were also obtained from 14 tryptic and 3 Staphylococcal V8 peptides. 3. 3. 10 peptides plus the N-terminal sequence were derived from a previously unsequenced protein which was distantly related to the product of the E. coli fadB gene (Baldwin G. S. (1993) Comp. Biochem. Physiol. 104B, 55–61). The remaining 7 peptides were derived from the gb-subunit of the gastric H + /K + -ATPase. 4. 4. The gastrin-binding activity remained in association with p78, and could be separated from the P-subunit of the gastric H + K + -ATPase, during chromatography on tomato lectin-Sepharose. 5. 5. We conclude that p78 binds gastrin, and is a novel member of the enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase family of enzymes.