title: Spinach nitrite reductase: subunit composition and siroheme redox potential.
abstract: The molecular weight of the spinach chloroplast, ferredoxin-dependent enzyme ferredoxin:nitrite oxidoreductase (EC 1.7.7.1) was shown to be 85,000 using gel filtration chromatography under nondenaturing conditions. In the presence of denaturants, either gel filtration chromatography or gel electrophoresis separated the enzyme into two subunits, with molecular weights of 61,000 and 24,000, respectively. Oxidation-reduction titrations of the siroheme prosthetic group of the putative native form (Mr 85,000) of the enzyme yielded a midpoint potential value of -305 mV, a value considerably more negative than the value of -30 mV obtained for siroheme in a modified, Mr 61,000 form of the enzyme.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University, Lubbock 79409-1061.
authors.forename: M
authors.initials: M
authors.lastname: Hirasawa
authors.forename: K A
authors.initials: KA
authors.lastname: Gray
authors.forename: J D
authors.initials: JD
authors.lastname: Sung
authors.forename: D B
authors.initials: DB
authors.lastname: Knaff
mesh_terms: D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D006418:Heme / Q000031:analogs & derivatives* / Q000378:metabolism; D046911:Macromolecular Substances; D008623:Mercaptoethanol / Q000494:pharmacology; D008970:Molecular Weight; D009247:NADH, NADPH Oxidoreductases / Q000302:isolation & purification*; D009572:Nitrite Reductases / Q000302:isolation & purification* / Q000378:metabolism; D010084:Oxidation-Reduction; D010944:Plants / Q000201:enzymology*
chemical_list: D046911:Macromolecular Substances; D006418:Heme; C009272:siroheme; D008623:Mercaptoethanol; D009247:NADH, NADPH Oxidoreductases; D009572:Nitrite Reductases