1jqf

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spinqualitylabelsall models 1jqf, resolution 1.85Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Human Transferrin N-Lobe Mutant H249Q

Contents 1 Overview 2 Disease 3 About this Structure 4 Reference

Overview

Proteins of the transferrin (Tf) family play a central role in iron, homeostasis in vertebrates. In vertebrate Tfs, the four iron-binding, ligands, 1 Asp, 2 Tyr, and 1 His, are invariant in both lobes of these, bilobal proteins. In contrast, there are striking variations in the Tfs, that have been characterized from insect species; in three of them, sequence changes in the C-lobe binding site render it nonfunctional, and, in all of them the His ligand in the N-lobe site is changed to Gln., Surprisingly, mutagenesis of the histidine ligand, His249, to glutamine in, the N-lobe half-molecule of human Tf (hTf/2N) shows that iron binding is, destabilized and suggests that Gln249 does not bind to iron. We have, determined the crystal structure of the H249Q mutant of hTf/2N and refined, it at 1.85 A resolution (R = 0.221, R(free) = 0.246). The structure, reveals that Gln249 does coordinate to iron, albeit with a lengthened, Fe-Oepsilon1 bond of 2.34 A. In every other respect, the protein structure, is unchanged from wild-type. Examination of insect Tf sequences shows that, the K206.K296 dilysine pair, which aids iron release from the N-lobes of, vertebrate Tfs, is not present in the insect proteins. We conclude that, substitution of Gln for His does destabilize iron binding, but in the, insect Tfs this is compensated by the loss of the dilysine interaction., The combination of a His ligand with the dilysine pair in vertebrate Tfs, may have been a later evolutionary development that gives more, sophisticated pH-mediated control of iron release from the N-lobe of, transferrins.

Disease

Known diseases associated with this structure: Atransferrinemia OMIM:[190000], Iron deficiency anemia, susceptibility to OMIM:[190000]

About this Structure

1JQF is a Single protein structure of sequence from Homo sapiens with CO3, FE and K as ligands. Full crystallographic information is available from OCA.

Reference

Ligand variation in the transferrin family: the crystal structure of the H249Q mutant of the human transferrin N-lobe as a model for iron binding in insect transferrins., Baker HM, Mason AB, He QY, MacGillivray RT, Baker EN, Biochemistry. 2001 Oct 2;40(39):11670-5. PMID:11570867

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