title: Crystal structure of a new type of NADPH-dependent quinone oxidoreductase (QOR2) from Escherichia coli.
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.
authors.affiliation: Laboratory of Biophysics, School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: In-Kwon
authors.initials: IK
authors.lastname: Kim
authors.forename: Hyung-Soon
authors.initials: HS
authors.lastname: Yim
authors.forename: Min-Kyu
authors.initials: MK
authors.lastname: Kim
authors.forename: Dong-Won
authors.initials: DW
authors.lastname: Kim
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Kim
authors.forename: Sun-Shin
authors.initials: SS
authors.lastname: Cha
authors.forename: Sa-Ouk
authors.initials: SO
authors.lastname: Kang
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009249:NADP / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011808:Quinone Reductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D029968:Escherichia coli Proteins; D005656:Fungal Proteins; C441635:NmrA protein, Aspergillus nidulans; D011994:Recombinant Proteins; D012097:Repressor Proteins; D009249:NADP; D011808:Quinone Reductases