1gvc

From Proteopedia

Revision as of 09:28, 20 March 2008

18KDA N-II DOMAIN FRAGMENT OF DUCK OVOTRANSFERRIN + NTA

Overview

In a previous paper [Lindley et al. (1993), Acta Cryst. D49, 292-304], the X-ray structure analysis of the 18 kDa fragment of duck ovotransferrin, corresponding to the NII domain of the intact protein, was reported at a resolution of 2.3 A. In this structure, the Fe(III) cation binds to two tyrosine residues and the synergistic carbonate anion in an identical manner to that found in the intact protein. However, the aspartate and histidine residues, normally involved in iron binding in transferrins, are absent in the fragment and it was not possible to unequivocally define what had replaced them. The electron density was tentatively assigned to be a mixture of peptides, presumably resulting from the proteolytic preparation of the fragment, binding to the iron through their amino and carboxylate termini. A more recent X-ray analysis of the fragment, from a different preparation, has resulted in a structure at 1.95 A, in which glycine appears to be the predominant residue bound to the cation. In an alternative attempt to clarify the binding of iron to the 18 kDa fragment, the metal was removed by dialysis and replaced in the form of ferric nitrilotriacetate. Crystallization of this complex has resulted in an X-ray structure at 1.90 A in which the Fe(III) is bound to the synergistic carbonate anion and only one tyrosine residue in a manner almost identical to the intact protein. The carboxylate groups and the tertiary amino group of the nitrilotriacetate occupy the remaining coordination sites. The second tyrosine residue, Tyr95, is not bound directly to the iron. The implication of these structures with respect to the mechanism of iron binding by the transferrins is addressed.

About this Structure

1GVC is a Single protein structure of sequence from Anas platyrhynchos. Full crystallographic information is available from OCA.

Reference

The mechanism of iron uptake by transferrins: the X-ray structures of the 18 kDa NII domain fragment of duck ovotransferrin and its nitrilotriacetate complex., Kuser P, Hall DR, Haw ML, Neu M, Evans RW, Lindley PF, Acta Crystallogr D Biol Crystallogr. 2002 May;58(Pt 5):777-83. Epub 2002, Apr 26. PMID:11976488

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