2h8d

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spinqualitylabelsall models 2h8d, resolution 1.78Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of deoxy hemoglobin from Trematomus bernacchii at pH 8.4

Overview

The Root effect is a widespread property in fish hemoglobins (Hbs) that, produces a drastic reduction of cooperativity and oxygen-binding ability, at acidic pH. Here, we report the high-resolution structure of the deoxy, form of Hb isolated from the Antarctic fish Trematomus bernacchii (HbTb), crystallized at pH 6.2 and 8.4. The structure at acidic pH has been, previously determined at a moderate resolution (Ito et al., J Mol Biol, 1995;250:648-658). Our results provide a clear picture of the events, occurring upon the pH increase from 6.2 to 8.4, observed within a, practically unchanged crystal environment. In particular, at pH 8.4, the, interaspartic hydrogen bond at the alpha(1)beta(2) interface is partially, broken, suggesting a pK(a) close to 8.4 for Asp95alpha. In addition, a, detailed survey of the histidine modifications, caused by the change in, pH, also indicates that at least three hot regions of the molecule are, modified (Ebeta helix, Cbeta-tail, CDalpha corner) and can be considered, to be involved at various levels in the release of the Root protons. Most, importantly, at the CDalpha corner, the break of the salt bridge, Asp48alpha-His55alpha allows us to describe a detailed mechanism that, transmits the modification from the CDalpha corner far to the alpha heme., More generally, the results shed light on the role played by the histidine, residues in modulating the strength of the Root effect and also support, the emerging idea that the structural determinants, at least for a part of, the Root effect, are specific of each Hb endowed with this property.

About this Structure

2H8D is a Protein complex structure of sequences from Trematomus bernacchii with , and as ligands. Full crystallographic information is available from OCA.

Reference

High resolution crystal structure of deoxy hemoglobin from Trematomus bernacchii at different pH values: the role of histidine residues in modulating the strength of the root effect., Mazzarella L, Vergara A, Vitagliano L, Merlino A, Bonomi G, Scala S, Verde C, di Prisco G, Proteins. 2006 Nov 1;65(2):490-8. PMID:16909420

Page seeded by OCA on Fri Feb 15 17:30:21 2008