title: Oxidation-reduction potentials of respiratory chain components in Thiobacillus A2.
abstract: (1) Cells of Thiobacillus A2 grown chemoautotrophically on thiosulfate or heterotrophically on succinate with oxygen contained b-, c-, o-, a- and a3-type cytochromes. The amount of cytochrome per mg of cell protein was much greater in thiosulfate-grown cells and differences in the relative concentrations of cytochromes were observed for the different growth conditions. (2) The half-reduction potentials at pH 7.0 (Em,7.0) and spectral maxima of c-, b-, a- and a3-type cytochromes were similar in cells grown aerobically with thiosulfate or with succinate as the growth substrate. (3) The half-reduction potential of the 'invisible', or high-potential copper, as determined from the potentiometric behavior of the carbon monoxide-reduced cytochrome a3 complex at pH 8.0, was 365 mV. (4) Reducing equivalents from thiosulfate appear to enter the respiratory chain at the cytochrome c level; however, studies in cell-free extracts were limited due to a loss in respiratory activity with thiosulfate as a substrate upon cell disruption.
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism; D017936:Cytochrome a Group; D003573:Cytochrome b Group; D003574:Cytochrome c Group / Q000378:metabolism; D003580:Cytochromes / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D013053:Spectrophotometry; D013855:Thiobacillus / Q000378:metabolism*; D013885:Thiosulfates / Q000378:metabolism
chemical_list: D017936:Cytochrome a Group; D003573:Cytochrome b Group; D003574:Cytochrome c Group; D003580:Cytochromes; D013885:Thiosulfates; D002248:Carbon Monoxide; D003576:Electron Transport Complex IV