Identification of the V factor needed for synthesis of the iron-molybdenum cofactor of nitrogenase as homocitrate.
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).
Hoover
T R
TR
Department of Biochemistry, University of Wisconsin-Madison 53706.
Robertson
A D
AD
Cerny
R L
RL
Hayes
R N
RN
Imperial
J
J
Shah
V K
VK
Ludden
P W
PW
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*
D005288:Ferredoxins; D008983:Molybdoferredoxin; D014233:Tricarboxylic Acids; C028143:homocitric acid; D009591:Nitrogenase