Kaim G, Dimroth P
Mikrobiologisches Institut, Eidgenössische Technische Hochschule, ETH-Zentrum, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland.
EMBO J. 1999 Aug 2;18(15):4118-27. doi: 10.1093/emboj/18.15.4118.
ATP synthase is the universal enzyme that manufactures cellular ATP using the energy stored in a transmembrane ion gradient. This energy gradient has two components: the concentration difference (DeltapH or DeltapNa(+)) and the electrical potential difference DeltaPsi, which are thermodynamically equivalent. However, they are not kinetically equivalent, as the mitochondrial and bacterial ATP synthases require a transmembrane potential, DeltaPsi, but the chloroplast enzyme has appeared to operate on DeltapH alone. Here we show that, contrary to the accepted wisdom, the 'acid bath' procedure used to study the chloroplast enzyme develops not only a DeltapH but also a membrane potential, and that this potential is essential for ATP synthesis. Thus, for the chloroplast and other ATP synthases, the membrane potential is the fundamental driving force for their normal operation. We discuss the biochemical reasons for this phenomenon and a model that is consistent with these new experimental facts.
ATP合酶是一种通用酶，它利用跨膜离子梯度中储存的能量来制造细胞ATP。这种能量梯度有两个组成部分：浓度差（ΔpH或ΔpNa⁺）和电势差ΔΨ，它们在热力学上是等效的。然而，它们在动力学上并不等效，因为线粒体和细菌的ATP合酶需要跨膜电势ΔΨ，但叶绿体酶似乎仅靠ΔpH就能发挥作用。在这里，我们表明，与普遍看法相反，用于研究叶绿体酶的“酸浴”程序不仅会产生ΔpH，还会产生膜电势，而且这种电势对于ATP合成至关重要。因此，对于叶绿体和其他ATP合酶来说，膜电势是其正常运作的基本驱动力。我们讨论了这种现象的生化原因以及与这些新实验事实相符的模型。
