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 μM, 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°C. We conclude that recombinant human progastrin6–80 selectively binds ferrous and ferric ions with high affinity in a stable 2:1 complex.
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Baldwin, G.S. Properties of the Complex Between Recombinant Human Progastrin and Ferric Ions. J Protein Chem 23, 65–70 (2004). https://doi.org/10.1023/B:JOPC.0000016259.59562.6c
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DOI: https://doi.org/10.1023/B:JOPC.0000016259.59562.6c