Accumulation of 55Fe-labeled precursors of the iron-molybdenum cofactor of nitrogenase on NifH and NifX of Azotobacter vinelandii.
Iron-molybdenum cofactor (FeMo-co) biosynthesis involves the participation of several proteins. We have used (55)Fe-labeled NifB-co, the specific iron and sulfur donor to FeMo-co, to investigate the accumulation of protein-bound precursors of FeMo-co. The (55)Fe label from radiolabeled NifB-co became associated with two major protein bands when the in vitro FeMo-co synthesis reaction was carried out with the extract of an Azotobacter vinelandii mutant lacking apodinitrogenase. One of the bands, termed (55)Fe-labeled upper band, was purified and shown to be NifH by immunoblot analysis. The (55)Fe-labeled lower band was identified as NifX by N-terminal sequencing. NifX purified from an A. vinelandii nifB strain showed a different electrophoretic mobility on anoxic native gels than did NifX with the FeMo-co precursor bound.
Department of Biochemistry and Center for the Study of Nitrogen Fixation, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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P
Rangaraj
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Ruttimann-Johnson
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Shah
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Ludden
D016948:Azotobacter vinelandii / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D005838:Genotype; D007501:Iron / Q000378:metabolism; D007504:Iron Radioisotopes; D018832:Molecular Chaperones / Q000378:metabolism; D008983:Molybdoferredoxin / Q000096:biosynthesis*; D009591:Nitrogenase / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*
D001426:Bacterial Proteins; C090993:HifB protein, Haemophilus influenzae; D007504:Iron Radioisotopes; D018832:Molecular Chaperones; D008983:Molybdoferredoxin; C118795:NifX protein, Bacteria; D007501:Iron; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase