title: A novel A3 group aconitase tolerates oxidation and nitric oxide.
abstract: Achromobacter denitrificans YD35 is an NO2 (-)-tolerant bacterium that expresses the aconitase genes acnA3, acnA4, and acnB, of which acnA3 is essential for growth tolerance against 100 mm NO2 (-). Atmospheric oxygen inactivated AcnA3 at a rate of 1.6 × 10(-3) min(-1), which was 2.7- and 37-fold lower compared with AcnA4 and AcnB, respectively. Stoichiometric titration showed that the [4Fe-4S](2+) cluster of AcnA3 was more stable against oxidative inactivation by ferricyanide than that of AcnA4. Aconitase activity of AcnA3 persisted against high NO2 (-) levels that generate reactive nitrogen species with an inactivation rate constant of k = 7.8 × 10(-3) min(-1), which was 1.6- and 7.8-fold lower than those for AcnA4 and AcnB, respectively. When exposed to NO2 (-), the acnA3 mutant (AcnA3Tn) accumulated higher levels of cellular citrate compared with the other aconitase mutants, indicating that AcnA3 is a major producer of cellular aconitase activity. The extreme resistance of AcnA3 against oxidation and reactive nitrogen species apparently contributes to bacterial NO2 (-) tolerance. AcnA3Tn accumulated less cellular NADH and ATP compared with YD35 under our culture conditions. The accumulation of more NO by AcnA3Tn suggested that NADH-dependent enzymes detoxify NO for survival in a high NO2 (-) milieu. This novel aconitase is distributed in Alcaligenaceae bacteria, including pathogens and denitrifiers, and it appears to contribute to a novel NO2 (-) tolerance mechanism in this strain.
authors.affiliation: From the Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Doi
authors.affiliation: From the Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan takaya.naoki.ge@u.tsukuba.ac.jp.
authors.forename: Naoki
authors.initials: N
authors.lastname: Takaya
mesh_terms: D042441:Achromobacter denitrificans / Q000201:enzymology*; D000154:Aconitate Hydratase / Q000737:chemistry*; D000255:Adenosine Triphosphate / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D005292:Ferricyanides / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D007527:Isoenzymes / Q000737:chemistry; D009154:Mutation; D009243:NAD / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry*; D010802:Phylogeny; D026361:Reactive Nitrogen Species; D011994:Recombinant Proteins / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D005292:Ferricyanides; D007506:Iron-Sulfur Proteins; D007527:Isoenzymes; D026361:Reactive Nitrogen Species; D011994:Recombinant Proteins; D009243:NAD; C007931:hexacyanoferrate III; D009569:Nitric Oxide; D000255:Adenosine Triphosphate; D000154:Aconitate Hydratase; D009584:Nitrogen; D010100:Oxygen
keywords: Alcaligenaceae; Bacterial Metabolism; Enzyme Inactivation; Iron-Sulfur Protein; Oxidative Stress; Reactive Nitrogen Species (RNS); Stress Response