Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, 2351319 Valparaíso, Chile.
Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136.
Proc Natl Acad Sci U S A. 2021 May 11;118(19). doi: 10.1073/pnas.2025556118.
The dissipation of acute acid loads by the voltage-gated proton channel (H1) relies on regulating the channel's open probability by the voltage and the ΔpH across the membrane (ΔpH = pH - pH). Using monomeric -H1, we asked whether ΔpH-dependent gating is produced during the voltage sensor activation or permeation pathway opening. A leftward shift of the conductance-voltage (G-V) curve was produced at higher ΔpH values in the monomeric channel. Next, we measured the voltage sensor pH dependence in the absence of a functional permeation pathway by recording gating currents in the monomeric nonconducting D160N mutant. Increasing the ΔpH leftward shifted the gating charge-voltage (Q-V) curve, demonstrating that the ΔpH-dependent gating in H1 arises by modulating its voltage sensor. We fitted our data to a model that explicitly supposes the H1 voltage sensor free energy is a function of both the proton chemical and the electrical potential. The parameters obtained showed that around 60% of the free energy stored in the ΔpH is coupled to the H1 voltage sensor activation. Our results suggest that the molecular mechanism underlying the H1 ΔpH dependence is produced by protons, which alter the free-energy landscape around the voltage sensor domain. We propose that this alteration is produced by accessibility changes of the protons in the H1 voltage sensor during activation.
通过电压门控质子通道（H1）耗散急性酸负荷依赖于通过电压和跨膜的 ΔpH（ΔpH = pH - pH）调节通道的开放概率。使用单体 -H1，我们询问 ΔpH 依赖性门控是否在电压传感器激活或渗透途径打开期间产生。在单体通道中，较高的 ΔpH 值会使电导-电压（G-V）曲线向左移动。接下来，我们通过记录单体非传导性 D160N 突变体中的门控电流，在没有功能性渗透途径的情况下测量电压传感器的 pH 依赖性。增加 ΔpH 值会使门控电荷-电压（Q-V）曲线向左移动，这表明 H1 中的 ΔpH 依赖性门控是通过调节其电压传感器产生的。我们将我们的数据拟合到一个模型中，该模型明确假设 H1 电压传感器的自由能是质子化学势和电势能的函数。得到的参数表明，储存在 ΔpH 中的自由能的约 60%与 H1 电压传感器的激活相关联。我们的结果表明，H1 ΔpH 依赖性的分子机制是由质子产生的，质子改变了电压传感器域周围的自由能景观。我们提出，这种改变是由质子在 H1 电压传感器激活过程中的可及性变化产生的。
