Complex I of Rhodobacter capsulatus and its role in reverted electron transport

被引:35
作者
Herter, SM [1 ]
Kortluke, CM [1 ]
Drews, G [1 ]
机构
[1] Univ Freiburg, Inst Biol 2, D-79104 Freiburg, Germany
关键词
Rhodobacter-capsulatus; complex I; reverted electron flow; NAD(+)-photoreduction; CO2; fixation; N-2; NuoE; NuoF;
D O I
10.1007/s002030050548
中图分类号
Q93 [微生物学];
学科分类号
071005 ; 100705 ;
摘要
The activities of NAD(+)-photoreduction and NADH/decyl-ubiquinone reductase in membrane preparations of Rhodobacter capsulatus changed to the same extent under different conditions. These results indicated that NADH:ubiquinone oxidoreductase (complex I) catalyzes the electron transport in the downhill direction (respiratory chain) and in the uphill direction (reverted electron flow). This conclusion was confirmed by the characterization of a complex-I-deficient mutant of R. capsulatus. The mutant was not able to reduce NAD(+) in the light. Since this mutant was not able to grow photoautotrophically, we concluded that complex I is the enzyme that catalyzes the reverted electron flow to NAD(+) to provide reduction equivalents for CO2 fixation. Complex I is not essential for the reverted electron flow to nitrogenase since the mutant grew under nitrogen-fixing conditions. As shown by immunological means, NuoE, a subunit of complex I from R. capsulatus having an extended C-terminus, was modified depending on the nitrogen source present in the growth medium. When the organism used N-2 instead of NH4+, a smaller NuoE polypeptide was synthesized. The complex-I-deficient mutant was not able to modify NuoE. The function of the modification is discussed.
引用
收藏
页码:98 / 105
页数:8
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