TY - JOUR
T1 - Ferric ions are essential for the biological activity of the hormone glycine-extended gastrin
AU - Pannequin, Julie
AU - Barnham, Kevin J.
AU - Hollande, Frédéric
AU - Shulkes, Arthur
AU - Norton, Raymond S.
AU - Baldwin, Graham S.
PY - 2002/12/13
Y1 - 2002/12/13
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=2242495394&partnerID=8YFLogxK
U2 - 10.1074/jbc.M208440200
DO - 10.1074/jbc.M208440200
M3 - Article
C2 - 12270941
AN - SCOPUS:2242495394
SN - 0021-9258
VL - 277
SP - 48602
EP - 48609
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 50
ER -