Sherratt H S
Department of Pharmacological Sciences, University of Newcastle upon Tyne, UK.
Rev Neurol (Paris). 1991;147(6-7):417-30.
Mitochondria are the main site of ATP synthesis in aerobic cells, using the free energy of the oxidation of metabolic fuels by oxygen. They have a matrix space containing the enzymes of the citrate cycle and beta-oxidation, enclosed by an inner membrane containing the 4 complexes of the electron transport chain, ATP synthase and specific carriers for metabolites. Mitochondria also have a relatively permeable outer membrane and an intermembrane space. ATP synthesis (oxidative phosphorylation) is critically dependent on the structural integrity of the mitochondrion. Electrons from substrate oxidations feed into the electron transport chain at complex I or complex II, and then successively flow to complex III, complex IV and finally to oxygen. Complexes I, III and IV are redox pumps and electron transport causes extrusion of protons from the matrix generating an electrochemical proton gradient (proton motive force) across the inner membrane. Protons return to the matrix 'through' ATP synthase driving the synthesis of ATP. The stoichiometry of proton extrusion and the yield of ATP are still uncertain. Mitochondria have genetic continuity and are inherited maternally. They possess a small amount of DNA which codes for some, but not all, of the subunits of complexes I, III, IV of ATP synthase. mtDNA also codes for mitochondrial ribosomal and messenger RNAs involved in the synthesis of mitochondrially coded subunits. All other mitochondrial peptides are synthesised on cytosolic ribosomes and are imported and targeted to their specific intramitochondrial locations, often after proteolytic removal of leader sequences.
线粒体是有氧细胞中ATP合成的主要场所，利用氧气氧化代谢燃料的自由能。它们有一个基质空间，包含柠檬酸循环和β-氧化的酶，被内膜包围，内膜含有电子传递链的4种复合物、ATP合酶和代谢物的特定载体。线粒体还有一个相对通透的外膜和一个膜间隙。ATP合成（氧化磷酸化）严重依赖于线粒体的结构完整性。底物氧化产生的电子在复合物I或复合物II处进入电子传递链，然后依次流向复合物III、复合物IV，最终流向氧气。复合物I、III和IV是氧化还原泵，电子传递导致质子从基质中挤出，在内膜上产生电化学质子梯度（质子动力）。质子通过ATP合酶返回基质，驱动ATP的合成。质子挤出的化学计量和ATP的产量仍不确定。线粒体具有遗传连续性，通过母系遗传。它们拥有少量DNA，编码ATP合酶复合物I、III、IV的一些但不是全部亚基。线粒体DNA还编码参与线粒体编码亚基合成的线粒体核糖体RNA和信使RNA。所有其他线粒体肽在胞质核糖体上合成，通常在蛋白酶去除前导序列后被导入并靶向到其特定的线粒体内位置。
