Ustilago maydis is an aerobic basidiomycete that depends on oxidative phosphorylation for its ATP supply, pointing to the mitochondrion as a key player in its energy metabolism. Mitochondrial respiratory complexes I, III2, and IV occur in supramolecular structures named respirasome. In this work, we characterized the subunit composition and the kinetics of NADH:Q oxidoreductase activity of the digitonine-solubilized respirasome (1600 kDa) and the free-complex I (990 kDa). In the presence of 2,6-dimethoxy-1,4-benzoquinone (DBQ) and cytochrome c, both the respirasome NADH:O2 and the NADH:DBQ oxidoreductase activities were inhibited by rotenone, antimycin A or cyanide. A value of 2.4 for the NADH oxidized/oxygen reduced ratio was determined for the respirasome activity, while ROS production was less than 0.001% of the oxygen consumption rate. Analysis of the NADH:DBQ oxidoreductase activity showed that respirasome was 3-times more active and showed higher affinity than free-complex I. The results suggest that the contacts between complexes I, III2 and IV in the respirasome increase the catalytic efficiency of complex I and regulate its activity to prevent ROS production.

中文翻译：

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线粒体呼吸体作为一个单元起作用，复合体I，III2和IV之间的串扰刺激了NADH脱氢酶的活性。

玉米粉虱是一种好氧的担子菌，其ATP的供应依赖于氧化磷酸化，表明线粒体是其能量代谢的关键因素。线粒体呼吸复合物I，III2和IV发生在称为呼吸小体的超分子结构中。在这项工作中，我们表征了洋地黄酮可溶呼吸体（1600 kDa）和游离复合体I（990 kDa）的亚基组成和动力学的NADH：Q氧化还原酶活性。在2,6-二甲氧基-1,4-苯醌（DBQ）和细胞色素c的存在下，鱼藤酮，抗霉素A或氰化物均抑制了呼吸道NADH：O2和NADH：DBQ氧化还原酶的活性。确定呼吸道活性的NADH氧化/氧还原率值为2.4，而ROS的产生量少于耗氧率的0.001％。