线粒体呼吸链复合体Ⅱ+Ⅲ的电子传递与质子转移的偶联

Coupling between Electron Transfer and Proton Pumping in Respiratory Chain ComplexⅡ+Ⅲof Rat Liver Mitochondria

研究了鼠肝线粒体内膜体呼吸链复合体Ⅱ＋Ⅲ的Ｈ~＋／２ｅ比与Δψ的相关性及其调节因素。证明：（１）用光谱法测得复合体Ⅱ＋Ⅲ的电子传递与质子转移初速度的Ｈ~＋／２ｅ比值接近４，与铁氰化钾脉冲法测得的结果相同。Ｈ~＋／２ｅ随着ΔμＨ~＋升高而逐渐下降。荧光透析法测定不同Ｆｅ^（３＋）还原速率建立的不同Δψ时，证明Ｈ~＋回漏对Δψ和Ｈ~＋泵出速度的依赖性。讨论了呼吸链复合体Ⅱ＋Ⅲ电子传递与质子转移之间的偶联以及“Ｒｅｄｏｘｓｌｉｐ”和“ｐｒｏｔｏｎｌｅａｋ”的现象。（２）抑制剂实验说明线粒体内膜中Ｃａ^（２＋）、Ｐｉ与Ｈ~＋的协同运输系统对线粒体内膜Ｈ~＋泵出及Ｈ~＋回漏作用有一定的调控作用。

A study on the relationship between H￣+/2e ratio and Δψ across inner mitochondrial membrane in rat liver mitochondria was carried out. Using both spectrophotometric titration and potassium ferricyanide pulse methods, the H￣+/2e ratio of respiratory chain complex Ⅱ+Ⅲ in rat liver mitochondria was determined to be 4.0. However, H￣+/2e ratios werefound to decrease with increase in ΔμH￣+. Experiment using Rhodomin 123 flow dialysis method showed that the initial rate of proton leak across inner mitohcondrial membrane were proton pumping-dependent and controlled by Δψ. Results from inhibitor experiments showed that Ca￣(2+)/H￣+ and Pi/H￣+ co-transport systems of inner mitochondrial membrane may play some role in regulating proton pumping and proton leak activities. In connection with these results mentioned above a discussion on the 'Redox slip' and 'Proton leak' in regulating coupling function of respiratory chain of mitochondria was presented.