1iq7
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Ovotransferrin, C-Terminal Lobe, Apo Form
OverviewOverview
The differential properties of anion-mediated Fe(3+) release between the, N- and C-lobes of transferrins have been a focus in transferrin, biochemistry. The structural and kinetic characteristics for isolated lobe, have, however, been documented with the N-lobe only. Here we demonstrate, for the first time the quantitative Fe(3+) release kinetics and the, anion-binding structure for the isolated C-lobe of ovotransferrin. In the, presence of pyrophosphate, sulfate, and nitrilotriacetate anions, the, C-lobe released Fe(3+) with a decelerated rate in a single exponential, progress curve, and the observed first order rate constants displayed a, hyperbolic profile as a function of the anion concentration. The profile, was consistent with a newly derived single-pathway Fe(3+) release model in, which the holo form is converted depending on the anion concentration into, a "mixed ligand" intermediate that releases Fe(3+). The apo C-lobe was, crystallized in ammonium sulfate solution, and the structure determined at, 2.3 A resolution demonstrated the existence of a single bound SO(4)(2-) in, the interdomain cleft, which interacts directly with Thr(461)-OG1, Tyr(431)-OH, and His(592)-NE2 and indirectly with Tyr(524)-OH. The latter, three groups are Fe(3+)-coordinating ligands, strongly suggesting the, facilitated Fe(3+) release upon the anion occupation at this site. The, SO(4)(2-) binding structure supported the single-pathway kinetic model.
About this StructureAbout this Structure
1IQ7 is a Single protein structure of sequence from Gallus gallus with NAG and SO4 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Anion-mediated Fe3+ release mechanism in ovotransferrin C-lobe: a structurally identified SO4(2-) binding site and its implications for the kinetic pathway., Mizutani K, Muralidhara BK, Yamashita H, Tabata S, Mikami B, Hirose M, J Biol Chem. 2001 Sep 21;276(38):35940-6. Epub 2001 Jul 20. PMID:11466309
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