title: Novel EPR signals associated with FeMoco centres of MoFe protein in MgADP-inhibited turnover of nitrogenase.
abstract: Two novel electron paramagnetic resonance (EPR) signals arising from the [1Mo-7Fe-9S-homocitrate] (FeMoco) centres of MoFe protein of Klebsiella pneumoniae nitrogenase (Kp1) were observed following turnover under MgATP-limited conditions. The combination of the nitrogenase Fe protein of Clostridium pasteurianum showed similar signals. The accumulation of MgADP under these conditions causes the normal EPR signal of dithionite-reduced Kp1 (with g=4.3, 3.6, 2.01) to be slowly converted to novel signals with g=4.74, 3.32, 2.00 and g=4.58, 3.50, 1.99. These signals do not form in incubation of protein mixtures containing only MgADP, thus they may be associated with trapped intermediates of the catalytic cycle.
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Colney, Norwich NR4 7UH, UK.
authors.forename: S
authors.initials: S
authors.lastname: Maritano
authors.forename: S A
authors.initials: SA
authors.lastname: Fairhurst
authors.forename: R R
authors.initials: RR
authors.lastname: Eady
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000737:chemistry; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology; D008982:Molybdenum / Q000737:chemistry; D008983:Molybdoferredoxin / Q000737:chemistry* / Q000378:metabolism*; D009591:Nitrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D008983:Molybdoferredoxin; D000244:Adenosine Diphosphate; D008982:Molybdenum; D007501:Iron; D009591:Nitrogenase