The mitochondrial respiratory chain is partially organized in a supercomplex assembly - Kinetic evidence using flux control analysis
The mitochondrial respiratory chain is partially organized in a supercomplex assembly - Kinetic evidence using flux control analysis
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DOI：
10.1074/jbc.m405135200
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发表时间：
2004-08-27
影响因子：
4.8
通讯作者：
Lenaz, G
中科院分区：
文献类型：
--
作者：
Bianchi, C;Genova, ML;Lenaz, G
其中酶复合物独立地嵌入线粒体内膜的脂质双层中并通过随机扩散的辅酶Q和细胞色素c连接的呼吸链模型最受青睐。然而，可以从哺乳动物线粒体中分离出多复合体单元，这表明复合体之间的直接电子通道模型。使用代谢通量控制分析的动力学测试可以区分两种模型：前一种模型意味着每种酶可能在不同程度上控制速率，而在后者中，整个代谢途径将表现为单个超复合物，并且抑制其任何一种组分都会引起相同的通量控制。特别是，在氧化磷酸化装置的其他组件（即ATP合酶，膜电位，载体）的情况下，超复合物的存在将引起每个呼吸复合物的流量控制系数接近1，所有系数的总和将远高于1。使用牛心脏线粒体和submitochondrial颗粒缺乏底物渗透性障碍，我们研究了涉及有氧NADH氧化（I，III，IV）和琥珀酸氧化（II，III，IV）的复合物的通量控制系数。复合物I和III被发现是高度的速率控制在NADH氧化，一个强有力的动力学证据表明存在的功能相关的两个复合物之间的关联，而复合物IV出现随机分布。此外，我们表明，复合物II是完全限速琥珀酸氧化，清楚地表明没有基板通道走向复合物III和IV。
The model of the respiratory chain in which the enzyme complexes are independently embedded in the lipid bilayer of the inner mitochondrial membrane and connected by randomly diffusing coenzyme Q and cytochrome c is mostly favored. However, multicomplex units can be isolated from mammalian mitochondria, suggesting a model based on direct electron channeling between complexes. Kinetic testing using metabolic flux control analysis can discriminate between the two models: the former model implies that each enzyme may be rate-controlling to a different extent, whereas in the latter, the whole metabolic pathway would behave as a single supercomplex and inhibition of any one of its components would elicit the same flux control. In particular, in the absence of other components of the oxidative phosphorylation apparatus (i.e. ATP synthase, membrane potential, carriers), the existence of a supercomplex would elicit a flux control coefficient near unity for each respiratory complex, and the sum of all coefficients would be well above unity. Using bovine heart mitochondria and submitochondrial particles devoid of substrate permeability barriers, we investigated the flux control coefficients of the complexes involved in aerobic NADH oxidation (I, III, IV) and in succinate oxidation (II, III, IV). Both Complexes I and III were found to be highly rate-controlling over NADH oxidation, a strong kinetic evidence suggesting the existence of functionally relevant association between the two complexes, whereas Complex IV appears randomly distributed. Moreover, we show that Complex II is fully rate-limiting for succinate oxidation, clearly indicating the absence of substrate channeling toward Complexes III and IV.