{"title":"The fully reduced terminal oxidase bd-I isolated from Escherichia coli binds cyanide","authors":"Vitaliy B. Borisov , Alexander M. Arutyunyan","doi":"10.1016/j.jinorgbio.2024.112653","DOIUrl":null,"url":null,"abstract":"<div><p>Cytochrome <em>bd</em>-I from <em>Escherichia coli</em> belongs to the superfamily of prokaryotic <em>bd</em>-type oxygen reductases. It contains three hemes, <em>b</em><sub>558</sub>, <em>b</em><sub>595</sub> and <em>d</em>, and couples oxidation of quinol by dioxygen with the generation of a proton-motive force. The enzyme exhibits resistance to various stressors and is considered as a target protein for next-generation antimicrobials. By using electronic absorption and MCD spectroscopy, this work shows that cyanide binds to heme <em>d</em><sup>2+</sup> in the isolated fully reduced cytochrome <em>bd</em>-I. Cyanide-induced difference absorption spectra display changes near the heme <em>d</em><sup>2+</sup> α-band, a minimum at 633 nm and a maximum around 600 nm, and a W-shaped response in the Soret region. Apparent dissociation constant (<em>K</em><sub>d</sub>) of the cyanide complex of heme <em>d</em><sup>2+</sup> is ∼0.052 M. Kinetics of cyanide binding is monophasic, indicating the presence of a single ligand binding site in the enzyme. Consistently, MCD data show that cyanide binds to heme <em>d</em><sup>2+</sup> but not to <em>b</em><sub>558</sub><sup>2+</sup> or <em>b</em><sub>595</sub><sup>2+</sup>. This agrees with the published structural data that the enzyme's active site is not a di-heme site. The observed rate of binding (<em>k</em><sub>obs</sub>) increases as the concentration of cyanide is increased, giving a second-order rate constant (<em>k</em><sub>on</sub>) of ∼0.1 M<sup>−1</sup> s<sup>−1</sup>.</p></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"259 ","pages":"Article 112653"},"PeriodicalIF":3.8000,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Inorganic Biochemistry","FirstCategoryId":"99","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0162013424001776","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"BIOCHEMISTRY & MOLECULAR BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Cytochrome bd-I from Escherichia coli belongs to the superfamily of prokaryotic bd-type oxygen reductases. It contains three hemes, b558, b595 and d, and couples oxidation of quinol by dioxygen with the generation of a proton-motive force. The enzyme exhibits resistance to various stressors and is considered as a target protein for next-generation antimicrobials. By using electronic absorption and MCD spectroscopy, this work shows that cyanide binds to heme d2+ in the isolated fully reduced cytochrome bd-I. Cyanide-induced difference absorption spectra display changes near the heme d2+ α-band, a minimum at 633 nm and a maximum around 600 nm, and a W-shaped response in the Soret region. Apparent dissociation constant (Kd) of the cyanide complex of heme d2+ is ∼0.052 M. Kinetics of cyanide binding is monophasic, indicating the presence of a single ligand binding site in the enzyme. Consistently, MCD data show that cyanide binds to heme d2+ but not to b5582+ or b5952+. This agrees with the published structural data that the enzyme's active site is not a di-heme site. The observed rate of binding (kobs) increases as the concentration of cyanide is increased, giving a second-order rate constant (kon) of ∼0.1 M−1 s−1.
期刊介绍:
The Journal of Inorganic Biochemistry is an established international forum for research in all aspects of Biological Inorganic Chemistry. Original papers of a high scientific level are published in the form of Articles (full length papers), Short Communications, Focused Reviews and Bioinorganic Methods. Topics include: the chemistry, structure and function of metalloenzymes; the interaction of inorganic ions and molecules with proteins and nucleic acids; the synthesis and properties of coordination complexes of biological interest including both structural and functional model systems; the function of metal- containing systems in the regulation of gene expression; the role of metals in medicine; the application of spectroscopic methods to determine the structure of metallobiomolecules; the preparation and characterization of metal-based biomaterials; and related systems. The emphasis of the Journal is on the structure and mechanism of action of metallobiomolecules.