Molecular mechanism of proton transport in CLC Cl-/H+ exchange transporters
Molecular mechanism of proton transport in CLC Cl-/H+ exchange transporters
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DOI：
10.1073/pnas.1205764109
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发表时间：
2012-07-17
影响因子：
11.1
通讯作者：
MacKinnon, Roderick
中科院分区：
文献类型：
--
作者：
Feng, Liang;Campbell, Ernest B.;MacKinnon, Roderick
CLC蛋白是肌肉、肾脏、骨骼和其他器官系统功能的基础，通过催化Cl-离子在细胞和细胞器膜上的运输。一些CLC蛋白是离子通道，而另一些则是将Cl-交换为H+的泵浦。Cl-离子穿过膜的途径已被表征，但H+的运输及其运动与Cl-运动耦合的原理尚不清楚。本研究表明，H+转运不仅取决于特定谷氨酸残基的存在，还取决于Cl-离子的存在。然而，在没有Cl-的情况下，通过将谷氨酸突变为丙氨酸并在溶液中加入含羧酸的分子，可以分离和分析H+的转运，这与通过羧酸基团进入阴离子途径介导H+转移的观点一致。氯离子和羧酸盐相互作用强烈。这些数据支持了一种机制，即谷氨酸羧酸盐作为Cl-离子的替代品，但它可以接受一个H+并在外部溶液和中心Cl-结合位点之间转移，再加上2个Cl-离子的运动。
CLC proteins underlie muscle, kidney, bone, and other organ system function by catalyzing the transport of Cl- ions across cell and organellar membranes. Some CLC proteins are ion channels while others are pumps that exchange Cl- for H+. The pathway through which Cl- ions cross the membrane has been characterized, but the transport of H+ and the principle by which their movement is coupled to Cl- movement is not well understood. Here we show that H+ transport depends not only on the presence of a specific glutamate residue but also the presence of Cl- ions. H+ transport, however, can be isolated and analyzed in the absence of Cl- by mutating the glutamate to alanine and adding carboxylate-containing molecules to solution, consistent with the notion that H+ transfer is mediated through the entry of a carboxylate group into the anion pathway. Cl- ions and carboxylate interact with each other strongly. These data support a mechanism in which the glutamate carboxylate functions as a surrogate Cl- ion, but it can accept a H+ and transfer it between the external solution and the central Cl- binding site, coupled to the movement of 2 Cl- ions.