Sholtz K F, Gorskaya I A, Kotelnikova A V
Eur J Biochem. 1983 Oct 17;136(1):129-34. doi: 10.1111/j.1432-1033.1983.tb07715.x.
The ratio of the number of protons transported directly by H+-ATPase of intact mitochondria and that of the hydrolyzed ATP (the proton translocation quotient) is determined. A special kinetic method which makes possible determination of ATPase and H+-translocase activities in the same experiment has been used to estimate the proton translocation quotient for mitochondrial H+-ATPase. The quotient is found to be, on average, equal to 3.31 mol/mol. It is shown that the protonophore 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile can greatly decrease the proton translocation quotient. This supports our assumption concerning a labile coupling between H+-translocase and ATPase in mitochondria [I. A. Gorskaya, K. F. Sholtz, S. A. Moreva, A. V. Kotelnikova (1979) Biochemistry (Engl. Transl. Biokhimiya) 44, 765-770]. A decrease in the translocation quotient in the presence of the protonophore is likely to be due to the ability of this uncoupler to take back the translocated protons into the mitochondrial matrix before their release into the medium. An electrostatic model of the molecular mechanism of H+-translocase and ATPase coupling in the H+-ATPase complex is discussed. The model is in agreement with the results obtained: transport of more than two protons per each hydrolyzed ATP molecule, and variable efficiency of the process.
测定完整线粒体中由H⁺-ATP酶直接转运的质子数与水解的ATP的质子数之比（质子转运商）。一种特殊的动力学方法，该方法使得在同一实验中能够测定ATP酶和H⁺-转位酶的活性，已被用于估算线粒体H⁺-ATP酶的质子转运商。发现该商平均等于3.31 mol/mol。结果表明，质子载体3,5-二叔丁基-4-羟基苄叉丙二腈可大大降低质子转运商。这支持了我们关于线粒体中H⁺-转位酶与ATP酶之间不稳定偶联的假设[I. A. 戈尔什卡娅、K. F. 肖尔茨、S. A. 莫列娃、A. V. 科捷利尼科娃（1979年）《生物化学》（英文译本《生物化学》）44, 765 - 770]。在质子载体存在下转运商的降低可能是由于这种解偶联剂能够在转运的质子释放到介质之前将其带回线粒体基质中。讨论了H⁺-ATP酶复合物中H⁺-转位酶与ATP酶偶联的分子机制的静电模型。该模型与所得结果一致：每个水解的ATP分子转运超过两个质子，且该过程效率可变。
