1p84

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[[Image:1p84.gif|left|200px]]
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{{STRUCTURE_1p84| PDB=1p84 | SCENE= }}
{{STRUCTURE_1p84| PDB=1p84 | SCENE= }}
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'''HDBT inhibited Yeast Cytochrome bc1 Complex'''
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===HDBT inhibited Yeast Cytochrome bc1 Complex===
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==Overview==
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Bifurcated electron transfer during ubiquinol oxidation is the key reaction of cytochrome bc1 complex catalysis. Binding of the competitive inhibitor 5-n-heptyl-6-hydroxy-4,7-dioxobenzothiazole to the Qo site of the cytochrome bc1 complex from Saccharomyces cerevisiae was analyzed by x-ray crystallography. This alkylhydroxydioxobenzothiazole is bound in its ionized form as evident from the crystal structure and confirmed by spectroscopic analysis, consistent with a measured pKa = 6.1 of the hydroxy group in detergent micelles. Stabilizing forces for the hydroxyquinone anion inhibitor include a polarized hydrogen bond to the iron-sulfur cluster ligand His181 and on-edge interactions via weak hydrogen bonds with cytochrome b residue Tyr279. The hydroxy group of the latter contributes to stabilization of the Rieske protein in the b-position by donating a hydrogen bond. The reported pH dependence of inhibition with lower efficacy at alkaline pH is attributed to the protonation state of His181 with a pKa of 7.5. Glu272, a proposed primary ligand and proton acceptor of ubiquinol, is not bound to the carbonyl group of the hydroxydioxobenzothiazole ring but is rotated out of the binding pocket toward the heme bL propionate A, to which it is hydrogen-bonded via a single water molecule. The observed hydrogen bonding pattern provides experimental evidence for the previously proposed proton exit pathway involving the heme propionate and a chain of water molecules. Binding of the alkyl-6-hydroxy-4,7-dioxobenzothiazole is discussed as resembling an intermediate step of ubiquinol oxidation, supporting a single occupancy model at the Qo site.
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(as it appears on PubMed at http://www.pubmed.gov), where 12782631 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12782631}}
==About this Structure==
==About this Structure==
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[[Category: Qo site]]
[[Category: Qo site]]
[[Category: Ubiquinol]]
[[Category: Ubiquinol]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 14:03:43 2008''

Revision as of 11:03, 29 July 2008

Template:STRUCTURE 1p84

HDBT inhibited Yeast Cytochrome bc1 Complex

Template:ABSTRACT PUBMED 12782631

About this Structure

1P84 is a Protein complex structure of sequences from Mus musculus and Saccharomyces cerevisiae. Full crystallographic information is available from OCA.

Reference

Structure of the yeast cytochrome bc1 complex with a hydroxyquinone anion Qo site inhibitor bound., Palsdottir H, Lojero CG, Trumpower BL, Hunte C, J Biol Chem. 2003 Aug 15;278(33):31303-11. Epub 2003 Jun 2. PMID:12782631

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