1tfa
From Proteopedia
OVOTRANSFERRIN, N-TERMINAL LOBE, APO FORM
Structural highlights
Function[TRFE_CHICK] Transferrins are iron binding transport proteins which can bind two Fe(3+) ions in association with the binding of an anion, usually bicarbonate. Responsible for the transport of iron from sites of absorption and heme degradation to those of storage and utilization. There are two forms of hen transferrin, ovotransferrin, found in the ovoducts and, serum transferrin, secreted by the liver. Serum transferrin may also have a role in stimulating cell proliferation and is regulated by iron levels. Ovotransferrin has a bacteriostatic function and, is not controlled by iron levels. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedTransferrins bind Fe3+ very tightly in a closed interdomain cleft by the coordination of four protein ligands (Asp60, Tyr92, Tyr191, and His250 in ovotransferrin N-lobe) and of a synergistic anion, physiologically bidentate CO32-. Upon Fe3+ uptake, transferrins undergo a large scale conformational transition: the apo structure with an opening of the interdomain cleft is transformed into the closed holo structure, implying initial Fe3+ binding in the open form. To solve the Fe3+-loaded, domain-opened structure, an ovotransferrin N-lobe crystal that had been grown as the apo form was soaked with Fe3+-nitrilotriacetate, and its structure was solved at 2.1 A resolution. The Fe3+-soaked form showed almost exactly the same overall open structure as the iron-free apo form. The electron density map unequivocally proved the presence of an iron atom with the coordination by the two protein ligands of Tyr92-OH and Tyr191-OH. Other Fe3+ coordination sites are occupied by a nitrilotriacetate anion, which is stabilized through the hydrogen bonds with the peptide NH groups of Ser122, Ala123, and Gly124 and a side chain group of Thr117. There is, however, no clear interaction between the nitrilotriacetate anion and the synergistic anion binding site, Arg121. Alternative structural state of transferrin. The crystallographic analysis of iron-loaded but domain-opened ovotransferrin N-lobe.,Mizutani K, Yamashita H, Kurokawa H, Mikami B, Hirose M J Biol Chem. 1999 Apr 9;274(15):10190-4. PMID:10187803[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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