ba₃ oxygen reductase from the thermohalophilic bacterium Rhodothermus marinus

• Published in: FEMS microbiology letters 2007-04, Vol.269 (1), p.41-47
• Main Authors: Veríssimo, Andreia F, Pereira, Manuela M, Melo, Ana M.P, Hreggvidsson, Gudmundur O, Kristjansson, Jakob Kr, Teixeira, Miguel
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - classification; Bacterial Proteins - genetics; Bacteriology; Biological and medical sciences; Copper; Copper - chemistry; cytochrome ba; cytochrome ba3; cytochrome oxidase; cytochrome-c oxidase; Electron transport; Fundamental and applied biological sciences. Psychology; Haem; Heme - chemistry; Metabolism. Enzymes; Microbiology; Molecular Sequence Data; Oxidation-Reduction; Oxidoreductases - chemistry; Oxidoreductases - classification; Oxidoreductases - genetics; Oxygen; Oxygen reductase; redox titration; Reductases; Rhodothermus - enzymology; Rhodothermus - genetics; Rhodothermus marinus; Sequence Alignment; Sequence Analysis, Protein; Stoichiometry; terminal oxidase
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1111/j.1574-6968.2006.00598.x

The aerobic respiratory chain of the thermohalophilic bacterium Rhodothermus marinus has been extensively studied. In this study the isolation and characterization of a third oxygen reductase expressed in this organism are described. This newly isolated enzyme is a typical member of the type B family of haem-copper oxygen reductases, showing 43% amino acid sequence identity and 63% similarity with the ba₃ oxygen reductase from Thermus thermophilus. It constitutes two subunits with apparent molecular masses of 42 and 38 kDa. It contains a low-spin B-type haem and a high-spin A-type haem. A stoichiometry of 1B: 1A haem per protein was obtained by spectral integration of UV-visible spectra. Metal analysis showed the presence of two iron and three copper ions, which is in agreement with the existence of a CuA centre. Taking advantage of having two spectroscopically distinct haems, the redox behaviour of the ba₃ oxygen reductase was analysed and discussed in the framework of a model with interacting centres. Both haems, B and A, present two transitions, have unusually low reduction potentials of -65 mV and an interaction potential of -52.5 mV.