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dc.contributor.authorBaldwin, Graham Sen
dc.contributor.authorCurtain, C Cen
dc.contributor.authorSawyer, W Hen
dc.identifier.citationBiochemistry; 40(36): 10741-6en
dc.description.abstractUptake of dietary iron is essential for replenishment of body stores. A role for the hormone gastrin in iron uptake as a chelator of ferric ions in the gastric lumen has been proposed previously [Baldwin, G. S. (1992) Med. Hypotheses 38, 70-74]. Here, spectroscopic evidence of selective, high-affinity binding of ferric ions to progastrin-derived peptides in aqueous solution at low pH is provided. The maximum at 281 nm in the absorption spectrum of glycine-extended gastrin(17) at pH 4.0 increased (2.07 +/- 0.30)-fold in the presence of > or =2 equiv of ferric ions. Titration of glycine-extended gastrin(17) with ferric ions under stoichiometric conditions indicated that the stoichiometry of binding was 2.00 +/- 0.28 mol of Fe(3+)/mol of peptide. Fluorescence quenching experiments yielded values for the stoichiometry and apparent dissociation constant of the ferric ion-glycine-extended gastrin(17) complex at pH 4.0 of 2.39 +/- 0.17 mol of Fe(3+)/mol and 0.62 +/- 0.19 microM, respectively. No interaction was detected with Co(2+), Cu(2+), Mn(2+), or Cr(3+). Electron paramagnetic resonance spectroscopy suggested that the iron ligands were either oxygen or sulfur atoms. Fluorescence quenching experiments with peptides derived from the glycine-extended gastrin(17) sequence indicated that one or more of the five glutamic acid residues were necessary for iron binding. The binding of ferric ions by glycine-extended gastrin(17) at low pH is consistent with a role for progastrin-derived peptides in iron uptake from the lumen of the gastrointestinal tract.en
dc.subject.otherBinding Sitesen
dc.subject.otherElectron Spin Resonance Spectroscopyen
dc.subject.otherFerric Compounds.chemistry.metabolismen
dc.subject.otherGastric Mucosa.metabolismen
dc.subject.otherGlutamic Aciden
dc.subject.otherHydrogen-Ion Concentrationen
dc.subject.otherModels, Biologicalen
dc.subject.otherProtein Conformationen
dc.subject.otherSpectrometry, Fluorescenceen
dc.titleSelective, high-affinity binding of ferric ions by glycine-extended gastrin(17).en
dc.typeJournal Articleen
dc.identifier.affiliationUniversity of Melbourne Department of Surgery, Austin Hospital, Melbourne, Victoria, Australiaen
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