Ferric ions are essential for the biological activity of the hormone glycine-extended gastrin

Julie Pannequin, Kevin J. Barnham, Frédéric Hollande, Arthur Shulkes, Raymond S. Norton, Graham S. Baldwin

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41 Citations (Scopus)

Abstract

Amidated and nonamidated gastrins elicit different biological effects via distinct receptors in different tissues. Amidated gastrin 17 stimulates gastric acid secretion and the development of gastric carcinoids, whereas glycine-extended gastrin 17 stimulates proliferation of the colonic mucosa and the development of colorectal cancers. Because glycine-extended gastrin 17 binds two ferric ions with high affinity (Baldwin, G. S., Curtain, C. C., and Sawyer, W. H. (2001) Biochemistry 40, 10741-10746), we have investigated the identity of the iron ligands and the role of ferric ions in biological activity. Here we report the solution structure of glycine-extended gastrin 17, determined by NMR spectroscopy. The spectral changes observed upon the addition of ferric ions revealed that Glu7 acted as a ligand at the first ferric binding site, and that Glu8 and Glu9 acted as ligands at the second ferric ion binding site. Fluorescence quenching experiments confirmed that a GglyE7A mutant bound only one ferric ion. The inability of this mutant to stimulate proliferation or migration in the IMGE-5 cell line and the observation that the iron chelator desferrioxamine selectively blocked the effects of glycine-extended gastrin 17 indicated that binding of a ferric ion to Glu7 was essential for biological activity. This is the first report of an essential role for a metal ion in the action of a hormone.

Original languageEnglish
Pages (from-to)48602-48609
Number of pages8
JournalThe Journal of Biological Chemistry
Volume277
Issue number50
DOIs
Publication statusPublished - 13 Dec 2002
Externally publishedYes

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