Biosynthesis of the iron-molybdenum cofactor of nitrogenase.
The iron-molybdenum cofactor (FeMo-co) of nitrogenase is a Mo-Fe-S cluster that has been proposed as the site of substrate reduction for the nitrogenase enzyme complex. Biosynthesis of FeMo-co in Klebsiella pneumoniae requires at least six nif (nitrogen fixation) gene products. One of the nif genes, nifV, apparently encodes a homocitrate synthase. The synthesis and accumulation of homocitrate [(R)-2-hydroxy-1,2,4-butanetricarboxylic acid] in K.pneumoniae is correlated to the presence of a functional nifV gene. K.pneumoniae strains with mutations in nifV synthesize and accumulate an aberrant form of FeMo-co. Nitrogenase from NifV- mutants is capable of reducing some of the substrates of nitrogenase effectively (e.g. acetylene), but reduces N2 poorly. With the aid of an in vitro FeMo-co synthesis system, it recently has been established that homocitrate is an endogenous component of FeMo-co. Substitution of homocitrate with other carboxylic acids results in the formation of aberrant forms of FeMo-co with altered substrate reduction capability.
Hoover
T R
TR
Department of Biochemistry, University of Wisconsin-Madison 53706.
Imperial
J
J
Ludden
P W
PW
Shah
V K
VK
D055598:Chemical Phenomena; D002621:Chemistry; D005288:Ferredoxins / Q000096:biosynthesis*; D007711:Klebsiella pneumoniae / Q000235:genetics; D008983:Molybdoferredoxin / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D014233:Tricarboxylic Acids / Q000037:antagonists & inhibitors / Q000378:metabolism
D005288:Ferredoxins; D008983:Molybdoferredoxin; D014233:Tricarboxylic Acids; C028143:homocitric acid