Thermodynamic and Kinetic Characterization of Electron‐Transfer Components in situ in Rhodopseudomonas spheroides and Rhodospirillum rubrum

作者：P. Leslie Dutton, J. BARRY JACKSON · 发表于：European Journal of Biochemistry · 年份：1972 · DOI：10.1111/j.1432-1033.1972.tb02121.x · 被引用次数：183 · 研究领域：Photosynthetic Processes and Mechanisms、Algal biology and biofuel production、Spectroscopy and Quantum Chemical Studies

The b‐ and c‐type cytochromes in chromatophores from photosynthetically grown Rhodospirillum rubrum and Rhodopseudomonas spheroides have been characterized in situ in terms of their oxidation‐reduction potential properties. In R. rubrum only one cytochrome c measured at 551—540 nm was resolved potentiometrically; the midpoint potential at pH 7.2, Em7.2, is +293 mV. Three cytochrome species measured at 562—540 nm were resolved; they had Em7.2 values + 170 mV, −5 mV and −105 mV and were tentatively identified with cytochrome b, cc′ and b respectively; they contributed to the over‐all absorbance change in the ratio 8:25:17, respectively. In Rps. spheroides the Em7.0 of cytochrome c is +295 mV. Three cytochromes tentatively considered to be of the b‐type have Em7.2 values of +155 mV, +50 mV and −90 mV; their approximate reduced minus oxidized maxima were determined to be 558—9 nm, 560 nm and 564 nm, respectively. The approximate relative absorbance ratio given at the reduced minus oxidized maxima was 8:21:14. The rapid oxidation‐reduction reactions of reaction‐center bacteriochlorophyll, cytochrome c and cytochromes bin Rps. spheroides measured following a 20‐nsec laser flash or a 200‐μsec xenon flash have been studied in the absence and presence of antimycin A as a function of oxidation‐reduction potential. The results indicated that the reaction‐center bacteriochlorophyll (Em7.0+ 450 mV) serves to oxidize the cytochrome c with a midpoint potential of 295 mV, cytochrome c295, (h...