Oxidation-reduction potentials of respiratory chain components in ThiobacillusA2 |
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Authors: | T.J. Kula M.I.H. Aleem David F. Wilson |
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Affiliation: | 1. School of Biological Sciences, University of Kentucky, Lexington, KY 40506 U.S.A.;2. Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104 U.S.A. |
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Abstract: | (1) Cells of ThiobacillusA2 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. |
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Keywords: | Respiratory chain Cytochrome Redox potential Thiosulfate TMPD To whom correspondence should be addressed. |
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