title: Properties of the complex between recombinant human progastrin and ferric ions.
abstract: Binding of ferric ions to the hormone glycine-extended gastrin17 is essential for biological activity (Pannequin, J., et al. (2002). J. Biol. Chem. 277: 48602-48609). The aims of the current study were to determine the properties of the complex between recombinant human progastrin6-80 and ferric ions. The stoichiometry and affinity of ferric ion binding were determined by fluorescence spectroscopy. The selectivity of metal ion binding and the stability of the 59Fe(III) progastrin6-80 complex were determined by equilibrium dialysis. The stoichiometry of 2.5 +/- 0.1 moles Fe/mole progastrin, and the apparent dissociation constant of 2.2 +/- 0.1 microM, were similar to the values previously determined for glycine-extended gastrin17 at pH 4.0. Of the four trivalent and seven divalent metal ions tested, only ferrous and ferric ions bound to progastrin6-80. The ferric ion-progastrin complex was extremely stable, with a half-life of 117 +/- 8 days at pH 7.6 and 25 degrees C. We conclude that recombinant human progastrin6-80 selectively binds ferrous and ferric ions with high affinity in a stable 2:1 complex.
authors.affiliation: University of Melbourne, Department of Surgery, Austin Campus, Austin, Australia. grahamsb@unimelb.edu.au
authors.forename: Graham S
authors.initials: GS
authors.lastname: Baldwin
mesh_terms: D001665:Binding Sites; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism*; D005755:Gastrins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D005290:Ferric Compounds; D005755:Gastrins; D011498:Protein Precursors; D011994:Recombinant Proteins; C013706:big gastrin