title: Active site structure of SoxB-type cytochrome bo3 oxidase from thermophilic Bacillus.
abstract: Two-subunit SoxB-type cytochrome c oxidase in Bacillus stearothermophilus was over-produced, purified, and examined for its active site structures by electron paramagnetic resonance (EPR) and resonance Raman (RR) spectroscopies. This is cytochrome bo3 oxidase containing heme B at the low-spin heme site and heme O at the high-spin heme site of the binuclear center. EPR spectra of the enzyme in the oxidized form indicated that structures of the high-spin heme O and the low-spin heme B were similar to those of SoxM-type oxidases based on the signals at g=6.1, and g=3.04. However, the EPR signals from the CuA center and the integer spin system at the binuclear center showed slight differences. RR spectra of the oxidized form showed that heme O was in a 6-coordinated high-spin (nu3 = 1472 cm(-1)), and heme B was in a 6-coordinated low-spin (nu3 = 1500 cm(-1)) state. The Fe2+-His stretching mode was observed at 211 cm(-1), indicating that the Fe2+-His bond strength is not so much different from those of SoxM-type oxidases. On the contrary, both the Fe2+-CO stretching and Fe2+-C-O bending modes differed distinctly from those of SoxM-type enzymes, suggesting some differences in the coordination geometry and the protein structure in the proximity of bound CO in cytochrome bo3 from those of SoxM-type enzymes.
authors.affiliation: Department of Biochemical Engineering and Science, Kyushu Institute of Technology, Iizuka, Fukuoka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Uchida
authors.forename: M
authors.initials: M
authors.lastname: Tsubaki
authors.forename: T
authors.initials: T
authors.lastname: Kurokawa
authors.forename: H
authors.initials: H
authors.lastname: Hori
authors.forename: J
authors.initials: J
authors.lastname: Sakamoto
authors.forename: T
authors.initials: T
authors.lastname: Kitagawa
authors.forename: N
authors.initials: N
authors.lastname: Sone
mesh_terms: D001665:Binding Sites; D003573:Cytochrome b Group; D003574:Cytochrome c Group / Q000737:chemistry; D003580:Cytochromes / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D029968:Escherichia coli Proteins; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D006418:Heme / Q000737:chemistry; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry; D021122:Protein Subunits; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014170:Transformation, Genetic
chemical_list: D003573:Cytochrome b Group; D003574:Cytochrome c Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; D021122:Protein Subunits; C083850:cytochrome bo3, E coli; D006418:Heme; D010088:Oxidoreductases; C064500:flavocytochrome c sulfide dehydrogenase; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV