Sottocasa G L, Kuylenstierna B, Ernster L, Bergstrand A
J Cell Biol. 1967 Feb;32(2):415-38. doi: 10.1083/jcb.32.2.415.
Preparations of rat-liver mitochondria catalyze the oxidation of exogenous NADH by added cytochrome c or ferricyanide by a reaction that is insensitive to the respiratory chain inhibitors, antimycin A, amytal, and rotenone, and is not coupled to phosphorylation. Experiments with tritiated NADH are described which demonstrate that this "external" pathway of NADH oxidation resembles stereochemically the NADH-cytochrome c reductase system of liver microsomes, and differs from the respiratory chain-linked NADH dehydrogenase. Enzyme distributation data are presented which substantiate the conclusion that microsomal contamination cannot account for the rotenone-insensitive NADH-cytochrome c reductase activity observed with the mitochondria. A procedure is developed, based on swelling and shrinking of the mitochondria followed by sonication and density gradient centrifugation, which permits the separation of two particulate subfractions, one containing the bulk of the respiratory chain components, and the other the bulk of the rotenone-insensitive NADH-cytochrome c reductase system. Morphological evidence supports the conclusion that the former subfraction consists of mitochondria devoid of outer membrane, and that the latter represents derivatives of the outer membrane. The data indicate that the electron-transport system associated with the mitochondrial outer membrane involves catalytic components similar to, or identical with, the microsomal NADH-cytochrome b(5) reductase and cytochrome b(5).
大鼠肝脏线粒体的制剂通过一种对呼吸链抑制剂抗霉素A、戊巴比妥和鱼藤酮不敏感且不与磷酸化偶联的反应，催化添加的细胞色素c或铁氰化物对外源性NADH的氧化。描述了用氚标记的NADH进行的实验，这些实验表明这种NADH氧化的“外部”途径在立体化学上类似于肝脏微粒体的NADH - 细胞色素c还原酶系统，并且不同于呼吸链相关联 的NADH脱氢酶。给出了酶分布数据来证实这样的结论：微粒体污染不能解释在线粒体中观察到的对鱼藤酮不敏感的NADH - 细胞色素c还原酶活性。基于线粒体的肿胀和收缩，随后进行超声处理和密度梯度离心，开发了一种方法，该方法允许分离两个颗粒亚组分，一个包含大部分呼吸链成分，另一个包含大部分对鱼藤酮不敏感的NADH - 细胞色素c还原酶系统。形态学证据支持这样的结论：前一个亚组分由没有外膜的线粒体组成，而后一个亚组分代表外膜的衍生物。数据表明与线粒体外膜相关的电子传递系统涉及与微粒体NADH - 细胞色素b5还原酶和细胞色素b5相似或相同的催化成分。
