Title An FMN-containing NADH-quinone reductase from streptomyces sp
Author Youn, Hong Duk · Lee, Jin Won · Youn, Hwan · Lee, Jeong Kug¹ · Hah, Yung Chil · Kang, Sa Ouk *
Address Department of Microbiology, College of Natural Sciences, and Research Center for Molecular Microbiology, Seoul National University; ¹Department of Biology, College of Sciences, Seogang University
Bibliography Journal of Microbiology, 34(2),206-213, 1996,
Key Words NADH-quinone reductase, FMN, semiquinone, Streptomyces sp
Abstract NADH-quinone reductase was purified 22-fold from the cytosolic fraction of Streptomyces sp. Imsnu-1 to apparent hemogenity, with an overall yield of 9%, by the purification procedure consisting of ammonium, sulfate precipitation and DEAE Sephacryl S-200 and DEAE 5 PW chromatographies. The molecular mass of the enzyme determined by gel filtration chromatography was found to be 110 kDa. SDS-PAGE revealed that the enzyme consists of two sugunits with a molecular mass of 54 kDa. The enzyme contained 1 mol of FMN per subunit as a cofactor. The A_272/A_457 ratio was 6.14 and the molar extinction coefficients were calculated to be 20, 800 and 25, 400M/sup -1/cm/sup -1/ AT 349 AND 457 nm, respectively. The N-terminal sequence of the enzyme contained the highly conserved fingerprint of ADP-binding domain. The enzyme used NADH as an electron donor and various quinones as electron acceptors. Cytochrome c was practically inactive. Air-stable flavin semiquinone was produced by the addition of NADH to the enzyme. Also, naphthosemiquinone was detected in the reaction mixture containing the enzyme.
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