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'''Crystal structure of the His145Ala mutant of 2,3-dihydroxybipheny dioxygenase (BphC)''' | '''Crystal structure of the His145Ala mutant of 2,3-dihydroxybipheny dioxygenase (BphC)''' | ||
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[[Category: Takahashi, Y.]] | [[Category: Takahashi, Y.]] | ||
[[Category: Uragami, Y.]] | [[Category: Uragami, Y.]] | ||
[[Category: | [[Category: Four time repetitions of the beta-alpha-beta-beta-beta motif]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 23:14:48 2008'' | |||
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Revision as of 23:14, 2 May 2008
Crystal structure of the His145Ala mutant of 2,3-dihydroxybipheny dioxygenase (BphC)
OverviewOverview
BphC derived from Pseudomonas sp. strain KKS102 is an extradiol-cleaving catecholic dioxygenase. This enzyme contains a non-heme iron atom and plays an important role in degrading biphenyl/polychlorinated biphenyls (PCBs) in the microbe. To elucidate detailed structures of BphC reaction intermediates, crystal structures of the substrate-free form, the BphC-substrate complex, and the BphC-substrate-NO (nitric oxide) complex were determined. These crystal structures revealed (1) the binding site of the O(2) molecule in the coordination sphere and (2) conformational changes of His194 during the catalytic reaction. On the basis of these findings, we propose a catalytic mechanism for the extradiol-cleaving catecholic dioxygenase in which His194 seems to play three distinct roles. At the early stage of the catalytic reaction, His194 appears to act as a catalytic base, which likely deprotonates the hydroxyl group of the substrate. At the next stage, the protonated His194 seems to stabilize a negative charge on the O2 molecule located in the hydrophobic O2-binding cavity. Finally, protonated His194 seems to function as a proton donor, whose existence has been proposed.
About this StructureAbout this Structure
1KWB is a Single protein structure of sequence from Pseudomonas sp.. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of the reaction intermediate and its homologue of an extradiol-cleaving catecholic dioxygenase., Sato N, Uragami Y, Nishizaki T, Takahashi Y, Sazaki G, Sugimoto K, Nonaka T, Masai E, Fukuda M, Senda T, J Mol Biol. 2002 Aug 23;321(4):621-36. PMID:12206778 Page seeded by OCA on Fri May 2 23:14:48 2008