2ibj

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Revision as of 10:06, 21 November 2007

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spinqualitylabelsall models 2ibj, resolution 1.550Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Structure of House Fly Cytochrome B5

Overview

We report a 1.55 A X-ray crystal structure of the heme-binding domain of, cytochrome b(5) from Musca domestica (house fly; HF b(5)), and compare it, with previously published structures of the heme-binding domains of bovine, microsomal cytochrome b(5) (bMc b(5)) and rat outer mitochondrial membrane, cytochrome b(5) (rOM b(5)). The structural comparison was done in the, context of amino acid sequences of all known homologues of the proteins, under study. We show that insect b(5)s contain an extended hydrophobic, patch at the base of the heme binding pocket, similar to the one, previously shown to stabilize mammalian OM b(5)s relative to their Mc, counterparts. The hydrophobic patch in insects includes a residue with a, bulky hydrophobic side chain at position 71 (Met). Replacing Met71 in HF, b(5) with Ser, the corresponding residue in all known mammalian Mc b(5)s, is found to substantially destabilize the holoprotein. The destabilization, is a consequence of two related factors: (1) a large decrease in, apoprotein stability and (2) extension of conformational disruption in the, apoprotein beyond the empty heme binding pocket (core 1) and into the, heme-independent folding core (core 2). Analogous changes have previously, been shown to accompany replacement of Leu71 in rOM b(5) with Ser. That, the stabilizing role of Met71 in HF b(5) is manifested primarily in the, apo state is highlighted by the fact that its crystallographic Calpha B, factor is modestly larger than that of Ser71 in bMc b(5), indicating that, it slightly destabilizes local polypeptide conformation when heme is in, its binding pocket. Finally, we show that the final unit of secondary, structure in the cytochrome b(5) heme-binding domain, a 3(10) helix known, as alpha6, differs substantially in length and packing interactions not, only for different protein isoforms but also for given isoforms from, different species. Proteins 2007. (c) 2007 Wiley-Liss, Inc.

About this Structure

2IBJ is a Single protein structure of sequence from Musca domestica with MG and HEM as ligands. Full crystallographic information is available from OCA.

Reference

Comparison of cytochromes b(5) from insects and vertebrates., Wang L, Cowley AB, Terzyan S, Zhang X, Benson DR, Proteins. 2007 Feb 13;. PMID:17299762

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