Abstract
Escherichia coli QOR2 [NAD(P)H-dependent quinone oxidoreductase; a ytfG gene product], which catalyzes two-electron reduction of methyl-1,4-benzoquinone, is a new type of quinone-reducing enzyme with distinct primary sequence and oligomeric conformation from previously known quinone oxidoreductases. The crystal structures of native QOR2 and the QOR2-NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) complex reveal that QOR2 consists of two domains (N-domain and C-domain) resembling those of NmrA, a negative transcriptional regulator that belongs to the short-chain dehydrogenase/reductase family. The N-domain, which adopts the Rossmann fold, provides a platform for NADPH binding, whereas the C-domain, which contains a hydrophobic pocket connected to the NADPH-binding site, appears to play important roles in substrate binding. Asn143 near the NADPH-binding site has been identified to be involved in substrate binding and catalysis from structural and mutational analyses. Moreover, compared with wild-type strain, the qor2-overexpressing strain shows growth retardation and remarkable decrease in several enzymes involved in carbon metabolism, suggesting that QOR2 could play some physiological roles in addition to quinone reduction.
Original language | English |
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Pages (from-to) | 372-384 |
Number of pages | 13 |
Journal | Journal of Molecular Biology |
Volume | 379 |
Issue number | 2 |
DOIs | |
State | Published - 29 May 2008 |
Bibliographical note
Funding Information:We thank Dr. Y.-J. Seok for valuable discussions on these experiments; Mr. H.I. Jung and Ms. S.M. Cho for assistance with the preparation of the manuscript; Drs. K.-S. Chae and S.-K. Chae for providing a cDNA library of As. Nidulans; and Dr. J.-H. Roe for providing a pTac3 expression vector. Work performed at the Seoul National University was supported by the 21C Frontier Microbial Genomics and Application Center Program, Ministry of Science and Technology (grant MG02-0201-001-1-0-0), Republic of Korea, and by research fellowship of the BK21 project. Work performed at the Korea Ocean Research and Development Institute was supported by a grant from the Functional Proteomics Center, the 21C Frontier Research and Development Program of the Korea Ministry of Science and Technology, Republic of Korea.
Keywords
- NAD(P)H-dependent quinone oxidoreductase
- QOR2
- carbon metabolism
- short-chain dehydrogenase/reductase family
- transcriptional regulator