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2ibj

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[[Image:2ibj.jpg|left|200px]]
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{{STRUCTURE_2ibj| PDB=2ibj | SCENE= }}
{{STRUCTURE_2ibj| PDB=2ibj | SCENE= }}
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'''Structure of House Fly Cytochrome B5'''
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===Structure of House Fly Cytochrome B5===
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==Overview==
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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.
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==About this Structure==
==About this Structure==
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[[Category: Fly cytochrome b5]]
[[Category: Fly cytochrome b5]]
[[Category: X-ray diffraction,heme]]
[[Category: X-ray diffraction,heme]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 07:17:47 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 14:37:04 2008''

Revision as of 11:37, 28 July 2008

Image:2ibj.png

Template:STRUCTURE 2ibj

Structure of House Fly Cytochrome B5

Template:ABSTRACT PUBMED 17299762

About this Structure

2IBJ is a Single protein structure of sequence from Musca domestica. Full crystallographic information is available from OCA.

Reference

Comparison of cytochromes b5 from insects and vertebrates., Wang L, Cowley AB, Terzyan S, Zhang X, Benson DR, Proteins. 2007 May 1;67(2):293-304. PMID:17299762

Page seeded by OCA on Mon Jul 28 14:37:04 2008

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