1i4y

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spinqualitylabelsall models 1i4y, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

THE CRYSTAL STRUCTURE OF PHASCOLOPSIS GOULDII WILD TYPE METHEMERYTHRIN

Overview

Reported are the X-ray crystal structures of recombinant Phascolopsis gouldii methemerythrin (1.8-A resolution) and the structure of an O2-binding-pocket mutant, L98Y methemerythrin (2.1-A resolution). The L98Y hemerythrin (Hr) has a greatly enhanced O2 affinity, a slower O2 dissociation rate, a larger solvent deuterium isotope effect on this rate, and a greater resistance to autoxidation relative to the wild-type protein. The crystal structures show that the hydrophobic binding pocket of Hr can accommodate substitution of a leucyl by a tyrosyl side chain with relatively minor structural rearrangements. UV/vis and resonance Raman spectra show that in solution L98Y methemerythrin contains a mixture of two diiron site structures differing by the absence or presence of an Fe(III)-coordinated phenolate. However, in the crystal, only one L98Y diiron site structure is seen, in which the Y98 hydroxyl is not a ligand, but instead forms a hydrogen bond to a terminal hydroxo/aqua ligand to the nearest iron. Based on this crystal structure, we propose that in the oxy form of L98Y hemerythrin the non-polar nature of the binding pocket favors localization of the Y98 hydroxyl near the O2 binding site, where it can donate a hydrogen bond to the hydroperoxo ligand. The stabilizing Y98OH-O2H-interaction would account for all of the altered O2 binding properties of L98Y Hr listed above.

About this Structure

1I4Y is a Single protein structure of sequence from Phascolopsis gouldii with and as ligands. Full crystallographic information is available from OCA.

Reference

The crystal structures of Phascolopsis gouldii wild type and L98Y methemerythrins: structural and functional alterations of the O2 binding pocket., Farmer CS, Kurtz DM Jr, Liu ZJ, Wang BC, Rose J, Ai J, Sanders-Loehr J, J Biol Inorg Chem. 2001 Apr;6(4):418-29. PMID:11372200

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