title: Electron flow and heme-heme interaction between cytochromes b-558, b-595 and d in a terminal oxidase of Escherichia coli.
abstract: The ESR signals of the cytochromes in the Escherichia coli terminal oxidase cytochrome d complex were studied at cryogenic temperature. The intensities and g values of the rhombic high-spin signals changed when the electronic state of cytochrome d was changed from the oxidized state to the reduced or oxygen-binding or CO-binding state. These rhombic signals were therefore assigned to cytochrome b-595, which is located near cytochrome d in the oxidase complex. This assignment was supported by the finding that the Em value of the rhombic signals differed from that of cytochrome d (Hata, A. et al. (1985) Biochim. Biophys. Acta 810, 62-72). Photolysis and ligand-exchange experiments with the reduced CO complex of the oxidase were performed in the presence of oxygen at -140 degrees C. The ESR spectra of three intermediate forms trapped by controlled low temperatures were detected. These forms were designated as the oxygen-binding intermediate I (ESR-silent), oxygen-binding intermediate II (giving ESR signals at g = 6.3, 5.5 and 2.15), and oxygen-binding intermediate III (giving signals at g = 6.3, 5.5 and 6.0). From these results, electron flow in the cytochrome d complex is proposed to proceed in the order, cytochrome b-558----cytochrome b-595----cytochrome d----O2. A model of the mechanism of four-electron chemistry for oxidation of ubiquinol-8 and formation of H2O by the cytochrome d complex is presented.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism; D003573:Cytochrome b Group / Q000378:metabolism*; D003580:Cytochromes / Q000378:metabolism*; D045263:Cytochromes a1; D004578:Electron Spin Resonance Spectroscopy; D045222:Electron Transport Chain Complex Proteins; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006418:Heme / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D019255:NADPH Oxidases; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011485:Protein Binding; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; D014451:Ubiquinone; D006418:Heme; D002248:Carbon Monoxide; D045263:Cytochromes a1; C036888:cytochrome b558; D010088:Oxidoreductases; D019255:NADPH Oxidases; C040077:cytochrome bd terminal oxidase complex, E coli; C003741:ubiquinol; D010100:Oxygen