title: Incorporation of iron and sulfur from NifB cofactor into the iron-molybdenum cofactor of dinitrogenase.
abstract: NifB-co is an iron- and sulfur-containing precursor to the iron-molybdenum cofactor (FeMo-co) of dinitrogenase. The synthesis of NifB-co requires at least the product of the nifB gene. Incorporation of 55Fe and 35S from NifB-co into FeMo-co was observed only when all components of the in vitro FeMo-co synthesis system were present. Incorporation of iron and sulfur from NifB-co into dinitrogenase was not observed in control experiments in which the apodinitrogenase (lacking FeMo-co) was initially activated with purified, unlabeled FeMo-co or in assays where NifB-co was oxygen-inactivated prior to addition to the synthesis system. These data clearly demonstrate that iron and sulfur from active NifB-co are specifically incorporated into FeMo-co of dinitrogenase and provide direct biochemical identification of an iron-sulfur precursor of FeMo-co. Under different in vitro FeMo-co synthesis conditions, iron and sulfur from NifB-co were associated with at least two other proteins (NIFNE and gamma) that are involved in the formation of active dinitrogenase. The results presented here suggest that multiple FeMo-co processing steps might occur on NIFNE and that FeMo-co synthesis is most likely completed prior to the association of FeMo-co with gamma.
authors.affiliation: Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Allen
authors.forename: R
authors.initials: R
authors.lastname: Chatterjee
authors.forename: P W
authors.initials: PW
authors.lastname: Ludden
authors.forename: V K
authors.initials: VK
authors.lastname: Shah
mesh_terms: D016948:Azotobacter vinelandii / Q000235:genetics / Q000378:metabolism; D004792:Enzyme Precursors / Q000737:chemistry / Q000378:metabolism; D005798:Genes, Bacterial; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D058085:Iron Compounds / Q000737:chemistry / Q000378:metabolism*; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D008983:Molybdoferredoxin / Q000737:chemistry / Q000378:metabolism*; D009591:Nitrogenase / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism
chemical_list: D004792:Enzyme Precursors; D058085:Iron Compounds; D008983:Molybdoferredoxin; C085381:NifB cofactor; D013455:Sulfur; D007501:Iron; D009591:Nitrogenase