The dissipation of acute acid loads by the voltage-gated proton channel (H_v1) relies on regulating the channel’s open probability by the voltage and the ΔpH across the membrane (ΔpH = pH_ex − pH_in). Using monomeric Ciona-H_v1, 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 H_v1 arises by modulating its voltage sensor. We fitted our data to a model that explicitly supposes the H_v1 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 H_v1 voltage sensor activation. Our results suggest that the molecular mechanism underlying the H_v1 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 H_v1 voltage sensor during activation.

电压门控质子通道 (H _v 1)对急性酸负荷的消散依赖于通过电压和跨膜的 ΔpH (ΔpH = pH _ex - pH _in )调节通道的开放概率。使用单体Ciona -H _v在图 1 中，我们询问在电压传感器激活或渗透通路打开过程中是否会产生 ΔpH 依赖性门控。在单体通道中较高的 ΔpH 值下产生电导-电压 (GV) 曲线的左移。接下来，我们通过记录单体非导电 D160N 突变体中的门控电流，在没有功能性渗透通路的情况下测量了电压传感器的 pH 值依赖性。增加 ΔpH 使门控电荷-电压 (QV) 曲线向左移动，表明 H _v 1中的 ΔpH 依赖门控是通过调节其电压传感器产生的。我们将数据拟合到一个模型中，该模型明确假设 H _v1 电压传感器自由能是质子化学和电势的函数。获得的参数表明，大约 60% 的 ΔpH 中存储的自由能与 H _v 1 电压传感器激活耦合。我们的结果表明，H _v 1 ΔpH 依赖性的分子机制是由质子产生的，它改变了电压传感器域周围的自由能景观。我们认为这种改变是由激活期间H _v 1 电压传感器中质子的可及性变化产生的。