title: Effect of nitric oxide on VnfA, a transcriptional activator of VFe-nitrogenase in Azotobacter vinelandii.
abstract: The transcriptional activator, VnfA, is necessary for the expression of the structural genes encoding vanadium-dependent nitrogenase in Azotobacter vinelandii. We have previously reported that VnfA harbours a Fe-S cluster as a prosthetic group, presumably a 3Fe-4S type, which is vital for the transcriptionally active VnfA. A plausible effector molecule is a reactive oxygen species (ROS), which disassembles the Fe-S cluster switching the active VnfA to become fully inactive. This finding prompted us to investigate the effect of nitric oxide (NO), another physiologically important radical species on the VnfA activity. Unlike ROS, the VnfA activity was moderately inhibited and converged to 70% of the maximum by NO irrespective of its concentration. The Fe-S cluster of VnfA was found to react with NO to form a dinitrosyl-iron complex, either in the dimeric or monomeric form, dependent on the relative stoichiometry of NO to the Fe-S cluster. The VnfA species harbouring the dinitrosyl-iron complexes in each form exhibited 50% ATPase activity compared to the active VnfA. The findings of this study would open an argument about a biological effect of NO on nitrogenase in light of its transcriptional regulatory system.
authors.affiliation: Department of Chemistry, Graduate School of Science; Graduate School of Bioagricultural Science; and Research Center of Materials Science, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Miura
authors.affiliation: Department of Chemistry, Graduate School of Science; Graduate School of Bioagricultural Science; and Research Center of Materials Science, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan.
authors.forename: Kyohei
authors.initials: K
authors.lastname: Yoshimitsu
authors.affiliation: Department of Chemistry, Graduate School of Science; Graduate School of Bioagricultural Science; and Research Center of Materials Science, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Takatani
authors.affiliation: Department of Chemistry, Graduate School of Science; Graduate School of Bioagricultural Science; and Research Center of Materials Science, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Watanabe
authors.affiliation: Department of Chemistry, Graduate School of Science; Graduate School of Bioagricultural Science; and Research Center of Materials Science, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan Department of Chemistry, Graduate School of Science; Graduate School of Bioagricultural Science; and Research Center of Materials Science, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan nakajima.hiroshi@f.mbox.nagoya-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakajima
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D009591:Nitrogenase / Q000378:metabolism*; D015534:Trans-Activators / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D015534:Trans-Activators; C090095:VnfA protein, Azotobacter vinelandii; D009569:Nitric Oxide; D009591:Nitrogenase
keywords: cluster; complex; dinitrosyl–iron; iron; nitric; nitrogenase; oxide; sulphur; transcriptional activator