1otv

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{{STRUCTURE_1otv| PDB=1otv | SCENE= }}
{{STRUCTURE_1otv| PDB=1otv | SCENE= }}
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'''PqqC, Pyrroloquinolinquinone Synthase C'''
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===PqqC, Pyrroloquinolinquinone Synthase C===
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==Overview==
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The biosynthesis of pyrroloquinoline quinone (PQQ), a vitamin and redox cofactor of quinoprotein dehydrogenases, is facilitated by an unknown pathway that requires the expression of six genes, pqqA to -F. PqqC, the protein encoded by pqqC, catalyzes the final step in the pathway in a reaction that involves ring cyclization and eight-electron oxidation of 3a-(2-amino-2-carboxyethyl)-4,5-dioxo-4,5,6,7,8,9-hexahydroquinoline-7,9-d icarboxylic-acid to PQQ. Herein, we describe the crystal structures of PqqC and its complex with PQQ and determine the stoichiometry of H2O2 formation and O2 uptake during the reaction. The PqqC structure(s) reveals a compact seven-helix bundle that provides the scaffold for a positively charged active site cavity. Product binding induces a large conformational change, which results in the active site recruitment of amino acid side chains proposed to play key roles in the catalytic mechanism. PqqC is unusual in that it transfers redox equivalents to molecular oxygen without the assistance of a redox active metal or cofactor. The structure of the enzyme-product complex shows additional electron density next to R179 and C5 of PQQ, which can be modeled as O2 or H2O2, indicating a site for oxygen binding. We propose a reaction sequence that involves base-catalyzed cyclization and a series of quinone-quinol tautomerizations that are followed by cycles of O2/H2O2-mediated oxidations.
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==About this Structure==
==About this Structure==
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[[Category: Pqq biosynthesis enzyme]]
[[Category: Pqq biosynthesis enzyme]]
[[Category: Seven helix bundle]]
[[Category: Seven helix bundle]]
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Revision as of 12:54, 28 July 2008

Image:1otv.png

Template:STRUCTURE 1otv

PqqC, Pyrroloquinolinquinone Synthase C

Template:ABSTRACT PUBMED 15148379

About this Structure

1OTV is a Single protein structure of sequence from Klebsiella pneumoniae. Full crystallographic information is available from OCA.

Reference

Quinone biogenesis: Structure and mechanism of PqqC, the final catalyst in the production of pyrroloquinoline quinone., Magnusson OT, Toyama H, Saeki M, Rojas A, Reed JC, Liddington RC, Klinman JP, Schwarzenbacher R, Proc Natl Acad Sci U S A. 2004 May 25;101(21):7913-8. Epub 2004 May 17. PMID:15148379

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