Functional Analysis of the Copper-Dependent Quercetin 2,3-Dioxygenase. 1. Ligand-Induced Coordination Changes Probed by X-ray Crystallography: Inhibition, Ordering Effect, and Mechanistic Insights

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• 作者：Roberto A. Steiner ; Ingeborg M. Kooter ; and Bauke W. Dijkstra
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：June 25, 2002
• 年：2002
• 卷：41
• 期：25
• 页码：7955 - 7962
• 全文大小：706K
• 年卷期：v.41,no.25(June 25, 2002)
• ISSN：1520-4995

文摘

The crystal structures of the copper-dependent Aspergillus japonicus quercetin 2,3-dioxygenase(2,3QD) complexed with the inhibitors diethyldithiocarbamate (DDC) and kojic acid (KOJ) are reportedat 1.70 and 2.15 Å resolution, respectively. Both inhibitors asymmetrically chelate the metal center andassume a common orientation in the active site cleft. Their molecular plane blocks access to the innerportion of the cavity which is lined by the side chains of residues Met51, Thr53, Phe75, Phe114, andMet123 and which is believed to bind the flavonol B-ring of the natural substrate. The binding of theinhibitors brings order into the mixed coordination observed in the native enzyme. DDC and KOJ inducea single conformation of the Glu73 side chain, although in different ways. In the presence of DDC, Glu73is detached from the copper ion with its carboxylate moiety pointing away from the active site cavity. Incontrast, when KOJ is bound, Glu73 ligates the Cu ion through its O¹ atom with a monodentate geometry.Compared to the native coordinating conformation, this conformation is approximately 90 rotated aboutthe ₃ angle. This latter Glu73 conformation is compatible with the presence of a bound substrate.