1IQ7

Ovotransferrin, C-Terminal Lobe, Apo Form

Summary for 1IQ7

• Entry DOI: 10.2210/pdb1iq7/pdb
• Related: 1TFA
• Descriptor: Ovotransferrin, 2-acetamido-2-deoxy-beta-D-glucopyranose, SULFATE ION, ... (4 entities in total)
• Functional Keywords: transferrin, ovotransferrin, iron binding protein, transport protein, metal transport
• Biological source: Gallus gallus (chicken)
• Total number of polymer chains: 1
• Total formula weight: 38738.90

Authors

Mizutani, K.,Muralidhara, B.K.,Yamashita, H.,Tabata, S.,Mikami, B.,Hirose, M. (deposition date: 2001-07-06, release date: 2001-11-28, Last modification date: 2024-10-09)

Primary citation

Mizutani, K.,Muralidhara, B.K.,Yamashita, H.,Tabata, S.,Mikami, B.,Hirose, M.
Anion-mediated Fe3+ release mechanism in ovotransferrin C-lobe: a structurally identified SO4(2-) binding site and its implications for the kinetic pathway.
J.Biol.Chem., 276:35940-35946, 2001

PubMed Abstract: 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.

PubMed: 11466309
DOI: 10.1074/jbc.M102590200

Experimental method

X-RAY DIFFRACTION (2.3 Å)