title: Inhibition of iron-molybdenum cofactor biosynthesis by L127Delta NifH and evidence for a complex formation between L127Delta NifH and NifNE.
abstract: Besides serving as the obligate electron donor to dinitrogenase during nitrogenase turnover, dinitrogenase reductase (NifH) is required for the biosynthesis of the iron-molybdenum cofactor (FeMo-co) and for the maturation of alpha(2)beta(2) apo-dinitrogenase (apo-dinitrogenase maturation). In an attempt to understand the role of NifH in FeMo-co biosynthesis, a site-specific altered form of NifH in which leucine at position 127 has been deleted, L127Delta, was employed in in vitro FeMo-co synthesis assays. This altered form of NifH has been shown to inhibit substrate reduction by the wild-type nitrogenase complex, forming a tight protein complex with dinitrogenase. The L127Delta NifH was found to inhibit in vitro FeMo-co synthesis by wild-type NifH as detected by the gamma gel shift assay. Increasing the concentration of NifNE and NifB-cofactor (NifB-co) relieved the inhibition of FeMo-co synthesis by L127Delta NifH. The formation of a complex of L127Delta NifH with NifNE was investigated by gel filtration chromatography. We herein report the formation of a complex between L127Delta NifH and NifNE in the presence of NifB-co. This work presents evidence for one of the possible roles for NifH in FeMo-co biosynthesis, i.e. the interaction of NifH with a NifNE.NifB-co complex.
authors.affiliation: Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: P
authors.initials: P
authors.lastname: Rangaraj
authors.forename: M J
authors.initials: MJ
authors.lastname: Ryle
authors.forename: W N
authors.initials: WN
authors.lastname: Lanzilotta
authors.forename: P J
authors.initials: PJ
authors.lastname: Goodwin
authors.forename: D R
authors.initials: DR
authors.lastname: Dean
authors.forename: V K
authors.initials: VK
authors.lastname: Shah
authors.forename: P W
authors.initials: PW
authors.lastname: Ludden
mesh_terms: D016948:Azotobacter vinelandii; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D017037:Dinitrogenase Reductase / Q000378:metabolism; D058085:Iron Compounds / Q000378:metabolism; D008983:Molybdoferredoxin / Q000096:biosynthesis* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009591:Nitrogenase / Q000235:genetics / Q000378:metabolism*; D010088:Oxidoreductases; D011485:Protein Binding
chemical_list: D001426:Bacterial Proteins; D017037:Dinitrogenase Reductase; D058085:Iron Compounds; D008983:Molybdoferredoxin; C085381:NifB cofactor; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase