Substrate binding mechanism of a type I extradiol dioxygenase

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Title
Substrate binding mechanism of a type I extradiol dioxygenase
Author(s)
H J Cho; K Kim; S Y Sohn; H Y Cho; K J Kim; Myung Hee Kim; D Kim; E Kim; B S Kang
Bibliographic Citation
Journal of Biological Chemistry, vol. 285, no. 45, pp. 34643-34652
Publication Year
2010
Abstract
A meta-cleavage pathway for the aerobic degradation of aromatic hydrocarbons is catalyzed by extradiol dioxygenases via a two-step mechanism: catechol substrate binding and dioxygen incorporation. The binding of substrate triggers the release of water, thereby opening a coordination site for molecular oxygen. The crystal structures of AkbC, a type I extradiol dioxygenase, and the enzyme substrate (3-methylcatechol) complex revealed the substrate binding process of extradiol dioxygenase. AkbC is composed of an N-domain and an active C-domain, which contains iron coordinated by a 2-His-1-carboxylate facial triad motif. The C-domain includes a β-hairpin structure and a C-terminal tail. In substrate-bound AkbC, 3-methylcatechol interacts with the iron via a single hydroxyl group, which represents an intermediate stage in the substrate binding process. Structure-based mutagenesis revealed that the C-terminal tail and β-hairpin form part of the substrate binding pocket that is responsible for substrate specificity by blocking substrate entry. Once a substrate enters the active site, these structural elements also play a role in the correct positioning of the substrate. Based on the results presented here, a putative substrate binding mechanism is proposed.
ISSN
0021-9258
Publisher
Amer Soc Biochemistry Molecular Biology Inc
DOI
http://dx.doi.org/10.1074/jbc.M110.130310
Type
Article
Appears in Collections:
Division of Biomedical Research > Microbiome Convergence Research Center > 1. Journal Articles
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