PDBsum entry 2d3i

Metal transport

PDB id: 2d3i

Contents

Protein chain

670 a.a. *

Ligands

BCT ×2

Metals

_AL ×2

Waters ×270

* Residue conservation analysis

PDB id:

2d3i

Name:

Metal transport

Title:

Crystal structure of aluminum-bound ovotransferrin at 2.15 angstrom resolution

Structure:

Ovotransferrin. Chain: a. Synonym: conalbumin, allergen gal d 3, gal d iii, serum transferrin

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Tissue: egg white

Resolution:

2.15Å R-factor: 0.206 R-free: 0.243

Authors:

K.Mizutani,B.Mikami,S.Aibara,M.Hirose

Key ref:

K.Mizutani et al. (2005). Structure of aluminium-bound ovotransferrin at 2.15 Angstroms resolution. Acta Crystallogr D Biol Crystallogr, 61, 1636-1642. PubMed id: 16301797 DOI: 10.1107/S090744490503266X

Date:

28-Sep-05 Release date: 29-Nov-05

Protein chain

P02789  (TRFE_CHICK) -  Ovotransferrin from Gallus gallus

Seq: 705 a.a.

Struc: 670 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

DOI no: 10.1107/S090744490503266X

Acta Crystallogr D Biol Crystallogr 61:1636-1642 (2005)

PubMed id: 16301797

Structure of aluminium-bound ovotransferrin at 2.15 Angstroms resolution.

K.Mizutani, B.Mikami, S.Aibara, M.Hirose.

ABSTRACT

Transferrin, well known as an iron-transport protein, can bind other metal ions, including toxic ones, and is considered to play an important role in the transportation of such metal ions. Here, a crystal structure of aluminium-bound transferrin is described for the first time. Colourless needle-shaped crystals of aluminium-bound ovotransferrin were obtained in PEG 400 solution. Structural determination was performed by molecular replacement using diferric (iron-bound) ovotransferrin as a model and the structural refinement was performed in the 50-2.15 Angstroms resolution range. The overall organization of the aluminium-bound form is almost the same as the iron-bound form: the protein is folded into two homologous lobes (N- and C-lobes) with two domains; two metal-binding sites are located within the inter-domain clefts of each lobe. Four residues (one Asp, two Tyr and one His) and one bicarbonate anion were found to bind an aluminium ion in either lobe, as in the iron-bound form. The highly similar domain-closed structure of the Al(3+)-bound form may permit the binding of Al(3+)-bound transferrin to the transferrin receptor. An unusual interaction, the dilysine trigger, which facilitates iron release at low pH in the endosome, was also found in the Al(3+)-bound form. These findings support the participation of transferrin in the transport of Al(3+) ions in vivo.

Selected figure(s)

Figure 3.
Figure 3 Stereo diagrams depicting the aluminium-binding sites. Electron-density maps (2F[o] - F[c], contoured at 1 [sigma] ; green) are shown for the Al3+-binding sites in (a) the N-lobe and (b) the C-lobe. Electron-density omit maps (F[o] - F[c], contoured at 3 [sigma] ; purple and orange) were calculated after refinement using a model in which Al3+ ions or bicarbonate anions were omitted. The final model is superimposed in a stick presentation with atoms in standard colours for the Al3+-coordinating residues (Asp60, Tyr92, Tyr191 and His250 for the N-lobe; Asp395, Tyr431, Tyr524 and His592 for the C-lobe) and bicarbonate anions. Al3+ atoms are shown by small spheres coloured cyan. The figures were prepared with the programs BobScript (Esnouf, 1999 [Esnouf, R. M. (1999). Acta Cryst. D55, 938-940.]-[bluearr.gif] ) and Raster3D (Merritt & Bacon, 1997 [Merritt, E. A. & Bacon, D. J. (1997). Methods Enzymol. 277, 505-524.]-[bluearr.gif] ).

The above figure is reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (2005, 61, 1636-1642) copyright 2005.

Figure was selected by an automated process.