title: Novel cyanide inhibition at cytochrome c1 of Rhodobacter capsulatus cytochrome bc1.
abstract: Oxidized cytochrome c(1) in photosynthetic bacterium Rhodobacter capsulatus cytochrome bc(1) reversibly binds cyanide with surprisingly high, micromolar affinity. The binding dramatically lowers the redox midpoint potential of heme c(1) and inhibits steady-state turnover activity of the enzyme. As cytochrome c(1), an auxiliary redox center of the high-potential chain of cytochrome bc(1), does not interact directly with the catalytic quinone/quinol binding sites Q(o) and Q(i), cyanide introduces a novel, Q-site independent locus of inhibition. This is the first report of a reversible inhibitor that manipulates the energetics and electron transfers of the high-potential redox chain of cytochrome bc(1), while maintaining quinone substrate catalytic sites in an intact form.
authors.affiliation: The Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, 1004 Stellar-Chance Building, 422 Curie Boulevard, Philadelphia, PA 19104, USA. osyczkaa@mail.med.upenn.edu
authors.forename: Artur
authors.initials: A
authors.lastname: Osyczka
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Moser
authors.forename: P Leslie
authors.initials: PL
authors.lastname: Dutton
mesh_terms: D001665:Binding Sites; D003486:Cyanides / Q000378:metabolism / Q000494:pharmacology*; D003575:Cytochromes c1 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry / Q000378:metabolism; D004734:Energy Metabolism; D010084:Oxidation-Reduction; D016354:Rhodobacter capsulatus / Q000378:metabolism; D013053:Spectrophotometry
chemical_list: D003486:Cyanides; D003575:Cytochromes c1; D014450:Electron Transport Complex III