The branched respiratory system of photosynthetically grown Rhodopseudomonas capsulata |
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Authors: | R.F. La Monica B.L. Marrs |
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Affiliation: | St. Louis University School of Medicine, St. Louis, Mo. 63104 U.S.A. |
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Abstract: | Various respiratory electron transport activities of Rhodopseudomonas capsulata were studied in membrane fragments prepared from photosynthetically grown cells of a parental strain and two terminal oxidase-defective mutant strains. The NADH and succinate oxidase activities of the mutant having a functional oxidase, M6, were considerably more sensitive to inhibition by either antimycin A or cyanide than the corresponding activities of the mutant lacking a functional oxidase, M7. The parental strain, Z-1, but not the mutants, showed biphasic inhibitory responses of NADH and succinate oxidase activities with either antimycin A or cyanide. In certain reactions no differences in inhibitor susceptibility were found among the strains tested, implying that the pathways involved were unaffected in the mutants. In this category were the actions of rotenone on NADH oxidase, antimycin A on cytochrome reductase and, in M6 and Z-1, cyanide on oxidase. These results suggest that the respiratory chain of the parental strain branches at the ubiquinone-cytochrome region into two pathways, each branch goes to a distinct terminal oxidase, and either may be blocked independently by genetic mutation. |
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Keywords: | TMPD |
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