CowN sustains nitrogenase turnover in the presence of the inhibitor carbon monoxide.

• 发表时间: Jan-Jun 2021
• 来源期刊: J Biol Chem
• DOI: 10.1016/j.jbc.2021.100501
• PMID: 33667548
• 文章类型: Journal Article
• 中科院分区: Q2
• 方向: 生物
• 作者列表: Medina MS,Bretzing KO,Aviles RA,Chong KM,Espinoza A,Garcia CNG,Katz BB,Kharwa RN,Hernandez A,Lee JL,Lee TM,Lo Verde C,Strul MW,Wong EY,Owens CP

关键词: Gluconacetobacter diazotrophicus; carbon monoxide; iron–sulfur cluster; iron–sulfur protein; nitrogen fixation; nitrogenase; protein–protein interaction

Mesh: Bacterial Proteins / chemistry metabolism; Carbon Monoxide / pharmacology; Catalysis; Gluconacetobacter / drug effects genetics metabolism; Kinetics; Models, Molecular; Nitrogen / metabolism; Nitrogen Fixation; Nitrogenase / chemistry metabolism; Oxidation-Reduction; Protein Interaction Domains and Motifs

Abstract

Nitrogenase is the only enzyme capable of catalyzing nitrogen fixation, the reduction of dinitrogen gas (N2) to ammonia (NH3). Nitrogenase is tightly inhibited by the environmental gas carbon monoxide (CO). Nitrogen-fixing bacteria rely on the protein CowN to grow in the presence of CO. However, the mechanism by which CowN operates is unknown. Here, we present the biochemical characterization of CowN and examine how CowN protects nitrogenase from CO. We determine that CowN interacts directly with nitrogenase and that CowN protection observes hyperbolic kinetics with respect to CowN concentration. At a CO concentration of 0.001 atm, CowN restores nearly full nitrogenase activity. Our results further indicate that CowN\'s protection mechanism involves decreasing the binding affinity of CO to nitrogenase\'s active site approximately tenfold without interrupting substrate turnover. Taken together, our work suggests CowN is an important auxiliary protein in nitrogen fixation that engenders CO tolerance to nitrogenase.