Properties of the complex between recombinant human progastrin and ferric ions

Protein J. 2004 Jan;23(1):65-70. doi: 10.1023/b:jopc.0000016259.59562.6c.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Ferric Compounds / chemistry*
  • Ferric Compounds / metabolism*
  • Gastrins / chemistry*
  • Gastrins / genetics
  • Gastrins / metabolism*
  • Humans
  • Kinetics
  • Protein Binding
  • Protein Precursors / chemistry*
  • Protein Precursors / genetics
  • Protein Precursors / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism

Substances

  • Ferric Compounds
  • Gastrins
  • Protein Precursors
  • Recombinant Proteins
  • big gastrin