title: The aerobic electron transport system of Eikenella corrodens.
abstract: The respiratory system of the fastidious beta-proteobacterium Eikenella corrodens grown with limited oxygen was studied. Membranes showed the highest oxidase activity with ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) or succinate and the lowest activity with NADH and formate. The presence of a bc1-type complex was suggested by the inhibition exerted by 2-heptyl-4-hydroxyquinoline-N-oxide (HOQNO), myxothiazol, and antimycin A on respiration with succinate and by the effect of the latter two inhibitors on the succinate-reduced difference spectra. Respiration with succinate or ascorbate-TMPD was abolished by low KCN concentrations, suggesting the presence of a KCN-sensitive terminal oxidase. Cytochromes b and c were spectroscopically detected after reduction with physiological or artificial electron donors, whereas type a and d cytochromes were not detected. The CO difference spectrum of membranes reduced by dithionite and its photodissociation spectrum (77 K) suggested the presence of a single CO compound that had the spectral features of a cytochrome o-like pigment. High-pressure liquid chromatography analysis of membrane haems confirmed the presence of haem B; in contrast, haems A and O were not detected. Peroxidase staining of membrane type c cytochromes using SDS-PAGE revealed the presence of five bands with apparent molecular masses of 44, 33, 30, 26, and 14 kDa. Based on our results, a tentative scheme of the respiratory chain in E. corrodens, comprising (i) dehydrogenases for succinate, NADH, and formate, (ii) a ubiquinone, (iii) a cytochrome bc1, and (iv) a type-cbb' cytochrome c oxidase, is proposed.
authors.affiliation: Grupo de Investigación in Biomembranes (GIBIOM), Facultad Ciencias de la Salud, Centro Seccional de Investigación (CIUL), Universidad Libre Seccional Barranquilla, Colombia. rjaramillo@unilibrebaq.edu.co
authors.forename: Rubén D
authors.initials: RD
authors.lastname: Jaramillo
authors.forename: Beatriz C
authors.initials: BC
authors.lastname: Barraza
authors.forename: Alma
authors.initials: A
authors.lastname: Polo
authors.forename: Martín
authors.initials: M
authors.lastname: Sará
authors.forename: Martha
authors.initials: M
authors.lastname: Contreras
authors.forename: J Edgardo
authors.initials: JE
authors.lastname: Escamilla
mesh_terms: D000332:Aerobiosis; D016124:Eikenella corrodens / Q000378:metabolism* / Q000502:physiology; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D006418:Heme / Q000737:chemistry; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D013053:Spectrophotometry; D013772:Tetramethylphenylenediamine / Q000378:metabolism
chemical_list: D006418:Heme; D003576:Electron Transport Complex IV; D013772:Tetramethylphenylenediamine