title: Identification of the V factor needed for synthesis of the iron-molybdenum cofactor of nitrogenase as homocitrate.
abstract: Nitrogenase catalyses the ATP-dependent reduction of N2 to NH3, and is composed of two proteins, dinitrogenase (MoFe protein or component I) and dinitrogenase reductase (Fe protein or component II). Dinitrogenase contains a unique prosthetic group (iron-molybdenum cofactor, FeMoco) comprised of Fe, Mo and S, which has been proposed as the site of N2 reduction. Biochemical and genetic studies of Nif- (nitrogen fixation) mutants of Klebsiella pneumoniae which are defective in nitrogen fixation, have shown that the nifB, nifQ, nifN, nifE and nifV genes are required for the biosynthesis of FeMo-co. Recently, a system for in vitro synthesis of FeMoco was described. The assay requires at least the nifB, nifN and nifE gene products, and a low-molecular-weight factor (V factor) produced in the presence of the nifV gene product. We have used this system to study FeMoco biosynthesis. We report here the isolation of V factor and identify it as homocitric acid ([R]2-hydroxy-1,2,4-butanetricarboxylic acid).
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison 53706.
authors.forename: T R
authors.initials: TR
authors.lastname: Hoover
authors.forename: A D
authors.initials: AD
authors.lastname: Robertson
authors.forename: R L
authors.initials: RL
authors.lastname: Cerny
authors.forename: R N
authors.initials: RN
authors.lastname: Hayes
authors.forename: J
authors.initials: J
authors.lastname: Imperial
authors.forename: V K
authors.initials: VK
authors.lastname: Shah
authors.forename: P W
authors.initials: PW
authors.lastname: Ludden
mesh_terms: D005288:Ferredoxins / Q000096:biosynthesis*; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000378:metabolism; D008983:Molybdoferredoxin / Q000096:biosynthesis* / Q000302:isolation & purification; D009591:Nitrogenase / Q000378:metabolism*; D014233:Tricarboxylic Acids / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D005288:Ferredoxins; D008983:Molybdoferredoxin; D014233:Tricarboxylic Acids; C028143:homocitric acid; D009591:Nitrogenase