title: Structure of the Zymomonas mobilis respiratory chain: oxygen affinity of electron transport and the role of cytochrome c peroxidase.
abstract: The genome of the ethanol-producing bacterium Zymomonas mobilis encodes a bd-type terminal oxidase, cytochrome bc1 complex and several c-type cytochromes, yet lacks sequences homologous to any of the known bacterial cytochrome c oxidase genes. Recently, it was suggested that a putative respiratory cytochrome c peroxidase, receiving electrons from the cytochrome bc1 complex via cytochrome c552, might function as a peroxidase and/or an alternative oxidase. The present study was designed to test this hypothesis, by construction of a cytochrome c peroxidase mutant (Zm6-perC), and comparison of its properties with those of a mutant defective in the cytochrome b subunit of the bc1 complex (Zm6-cytB). Disruption of the cytochrome c peroxidase gene (ZZ60192) caused a decrease of the membrane NADH peroxidase activity, impaired the resistance of growing culture to exogenous hydrogen peroxide and hampered aerobic growth. However, this mutation did not affect the activity or oxygen affinity of the respiratory chain, or the kinetics of cytochrome d reduction. Furthermore, the peroxide resistance and membrane NADH peroxidase activity of strain Zm6-cytB had not decreased, but both the oxygen affinity of electron transport and the kinetics of cytochrome d reduction were affected. It is therefore concluded that the cytochrome c peroxidase does not terminate the cytochrome bc1 branch of Z. mobilis, and that it is functioning as a quinol peroxidase.
authors: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia.
authors: Elina
authors: E
authors: Balodite
authors: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia.
authors: Inese
authors: I
authors: Strazdina
authors: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia.
authors: Nina
authors: N
authors: Galinina
authors: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors: Samantha
authors: S
authors: McLean
authors: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia.
authors: Reinis
authors: R
authors: Rutkis
authors: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors: Robert K
authors: RK
authors: Poole
authors: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda boulv. 4, 1586 Riga, Latvia.
authors: Uldis
authors: U
authors: Kalnenieks
mesh_terms: D003578:Cytochrome-c Peroxidase / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport / Q000235:genetics*; D017353:Gene Deletion; D010088:Oxidoreductases / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D017355:Zymomonas / Q000235:genetics*
chemical_list: D010088:Oxidoreductases; C020094:duroquinol oxidase; D003578:Cytochrome-c Peroxidase; D010100:Oxygen