Anoxic function for the Escherichia coli flavohaemoglobin (Hmp): reversible binding of nitric oxide and reduction to nitrous oxide

FEBS Letters

Lloyd, David¹  Poole, Robert K.⁴  Hughes, Martin N.³  Kim, Sung Oog⁴  Orii, Yutaka² 

[1] School of Pure and Applied Biology, University of Wales, P.O. Box 915, Cardiff CF1 3TL, UK;Department of Public Health, Graduate School of Medicine, Kyoto University, Kyoto 606, Japan;Department of Chemistry, King's College London, Strand, London WC2R 2LS, UK;Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Sheffield S10 2TN, UK

关键词: Hemoglobin (Escherichia coli);    Flavohaemoglobin;    Nitric oxide;    Nitric oxide reductase;    Bacterial nitric oxide detoxification;   

DOI  :  10.1016/S0014-5793(99)00157-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The flavohaemoglobin Hmp of Escherichia coli is inducible by nitric oxide (NO) and provides protection both aerobically and anaerobically from inhibition of growth by NO and agents that cause nitrosative stress. Here we report rapid kinetic studies of NO binding to Fe(III) Hmp with a second order rate constant of 7.5×10⁵ M⁻¹ s⁻¹ to generate a nitrosyl adduct that was stable anoxically but decayed in the presence of air to reform the Fe(III) protein. NO displaced CO bound to dithionite-reduced Hmp but, remarkably, CO recombined after only 2 s at room temperature indicative of NO reduction and dissociation from the haem. Addition of NO to anoxic NADH-reduced Hmp also generated a nitrosyl species which persisted while NADH was oxidised. These results are consistent with direct demonstration by membrane-inlet mass spectrometry of NO consumption and nitrous oxide production during anoxic incubation of NADH-reduced Hmp. The results demonstrate a new mechanism by which Hmp may eliminate NO under anoxic growth conditions.

【 授权许可】

Unknown