Institute for Advanced Simulation (IAS-5) and Institute of Neuroscience and Medicine (INM-9), Computational Biomedicine, Forschungszentrum Jülich, 52425 Jülich, Germany.
Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, Forschungszentrum Jülich, 52425 Jülich, Germany.
J Phys Chem Lett. 2021 May 13;12(18):4415-4420. doi: 10.1021/acs.jpclett.1c00361. Epub 2021 May 5.
The CLC family of anion channels and transporters includes Cl/H exchangers (blocked by F) and F/H exchangers (or CLCs). CLCs contain a glutamate (E318) in the central anion-binding site that is absent in CLC Cl/H exchangers. The X-ray structure of the protein from (CLC-eca) shows that E318 tightly binds to F when the gating glutamate (E118; highly conserved in the CLC family) faces the extracellular medium. Here, we use classical and DFT-based QM/MM metadynamics simulations to investigate proton transfer and release by CLC-eca. After to movement of protonated E118, both glutamates combine with F to form a triad, from which protons and F anions are released as HF. Our results illustrate how glutamate insertion into the central anion-binding site of CLC-eca permits the release of H to the cytosol as HF, thus enabling a net 1:1 F/H stoichiometry.
CLC 家族的阴离子通道和转运蛋白包括 Cl/H 交换体（被 F 阻断）和 F/H 交换体（或 CLCs）。CLC 包含一个位于中央阴离子结合位点的谷氨酸（E318），而 CLC Cl/H 交换体中不存在该谷氨酸。来自 （CLC-eca）的蛋白质的 X 射线结构表明，当门控谷氨酸（E118；在 CLC 家族中高度保守）面向细胞外介质时，E318 与 F 紧密结合。在这里，我们使用经典和基于 DFT 的 QM/MM 元动力学模拟来研究 CLC-eca 的质子转移和释放。质子化的 E118 后，两个谷氨酸与 F 结合形成三联体，质子和 F 阴离子从其中释放出来形成 HF。我们的结果说明了谷氨酸如何插入 CLC-eca 的中央阴离子结合位点，从而允许 H 以 HF 的形式释放到细胞质中，从而实现 1:1 的 F/H 化学计量比。
