1i4z
From Proteopedia
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THE CRYSTAL STRUCTURE OF PHASCOLOPSIS GOULDII L98Y 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
1I4Z is a Single protein structure of sequence from Phascolopsis gouldii with FEO as ligand. 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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