Download MendeleyAlternative 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.(1999) J Biol Chem 274: 10190-10194
- PubMed: 10187803
- DOI: https://doi.org/10.1074/jbc.274.15.10190
- Primary Citation of Related Structures:
1NFT, 1TFA - PubMed Abstract:
Transferrins 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.
Organizational Affiliation:
Research Institute for Food Science, Kyoto University, Uji, Kyoto 6110011, Japan.
