Kaim G
Institut für Mikrobiologie, Eidgenössische Technische Hochschule, ETH-Zentrum, Schmelzbergstrasse 7, CH-8092, Zürich, Switzerland.
Biochim Biophys Acta. 2001 May 1;1505(1):94-107. doi: 10.1016/s0005-2728(00)00280-2.
The ATP synthase of Propionigenium modestum encloses a rotary motor involved in the production of ATP from ADP and inorganic phosphate utilizing the free energy of an electrochemical Na(+) ion gradient. This enzyme clearly belongs to the family of F(1)F(0) ATP synthases and uses exclusively Na(+) ions as the physiological coupling ion. The motor domain, F(0), comprises subunit a and the b subunit dimer which are part of the stator and the subunit c oligomer acting as part of the rotor. During ATP synthesis, Na(+) translocation through F(0) proceeds from the periplasm via the stator channel (subunit a) onto a Na(+) binding site of the rotor (subunit c). Upon rotation of the subunit c oligomer versus subunit a, the occupied rotor site leaves the interface with the stator and the Na(+) ion can freely dissociate into the cytoplasm. Recent experiments demonstrate that the membrane potential is crucial for ATP synthesis under physiological conditions. These findings support the view that voltage generates torque in F(0), which drives the rotation of the gamma subunit thus liberating tightly bound ATP from the catalytic sites in F(1). We suggest a mechanochemical model for the transduction of transmembrane Na(+)-motive force into rotary torque by the F(0) motor that can account quantitatively for the experimental data.
中度嗜丙酸菌的ATP合酶包含一个旋转马达，该马达利用电化学钠离子梯度的自由能，将ADP和无机磷酸转化为ATP。这种酶显然属于F(1)F(0) ATP合酶家族，并且仅使用钠离子作为生理偶联离子。马达结构域F(0)由作为定子一部分的a亚基和b亚基二聚体以及作为转子一部分的c亚基寡聚体组成。在ATP合成过程中，钠离子通过F(0)从周质经定子通道（a亚基）转运到转子（c亚基）的钠离子结合位点上。随着c亚基寡聚体相对于a亚基的旋转，被占据的转子位点离开与定子的界面，钠离子可以自由解离进入细胞质。最近的实验表明，膜电位在生理条件下对ATP合成至关重要。这些发现支持了这样一种观点，即电压在F(0)中产生扭矩，驱动γ亚基旋转，从而从F(1)中的催化位点释放紧密结合的ATP。我们提出了一个机械化学模型，用于解释F(0)马达如何将跨膜钠离子驱动力转化为旋转扭矩，该模型能够定量解释实验数据。
