PDBsum entry 1gv8

Iron transport

PDB id: 1gv8

Contents

Protein chain

159 a.a. *

Ligands

GLY

CO3

Metals

_FE

Waters ×116

* Residue conservation analysis

PDB id:

1gv8

Name:

Iron transport

Title:

18 kda fragment of n-ii domain of duck ovotransferrin

Structure:

Ovotransferrin. Chain: a. Fragment: nii fragment, residues 91-249

Source:

Anas platyrhynchos. Common duck. Organism_taxid: 8839

Resolution:

1.95Å R-factor: 0.171 R-free: 0.218

Authors:

P.Kuser,D.R.Hall,M.L.Haw,M.Neu,P.F.Lindley

Key ref:

P.Kuser et al. (2002). 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. Acta Crystallogr D Biol Crystallogr, 58, 777-783. PubMed id: 11976488 DOI: 10.1107/S0907444902003724

Date:

07-Feb-02 Release date: 12-Feb-02

Protein chain

P56410  (TRFE_ANAPL) -  Ovotransferrin from Anas platyrhynchos

Seq: 686 a.a.

Struc: 159 a.a.*

* PDB and UniProt seqs differ at 6 residue positions (black crosses)

DOI no: 10.1107/S0907444902003724

Acta Crystallogr D Biol Crystallogr 58:777-783 (2002)

PubMed id: 11976488

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.

P.Kuser, D.R.Hall, M.L.Haw, M.Neu, R.W.Evans, P.F.Lindley.

ABSTRACT

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.

Selected figure(s)

Figure 1.
Figure 1 A ribbon diagram of the 18 kDa fragment of duck ovotransferrin corresponding to the NII domain. The location of the synergistic carbonate anion and the ferric cation at the N-terminus of the helix formed by residues 124-134, helix 5, is clearly shown together with tyrosine residues Tyr95 and Tyr188. The remaining ligands to the iron have been omitted (see Figs. 2-and 3-), but the exposure of the cation to the solvent is apparent. The poorly defined loop region, 144-149, is at the left-hand side of the diagram, immediately following helix 5.

The above figure is reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (2002, 58, 777-783) copyright 2002.

Figure was selected by an automated process.