Temperature dependence of proton permeation through a voltage-gated proton channel
Temperature dependence of proton permeation through a voltage-gated proton channel
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DOI：
10.1085/jgp.200910213
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发表时间：
2009-09-01
影响因子：
3.8
通讯作者：
Oiki, Shigetoshi
中科院分区：
文献类型：
--
作者：
Kuno, Miyuki;Ando, Hiroyuki;Oiki, Shigetoshi
电压门控质子通道存在于许多不同类型的细胞中，它们促进质子通过细胞膜的运动。质子通过通道渗透的机制是一个长期感兴趣的问题，但它仍然是一个悬而未决的问题。为了解决这个问题，我们研究了质子渗透的温度依赖性。在全细胞记录下，在几毫秒内施加快速的温度变化。这种方法允许在温度跳跃之前和之后立即测量电流振幅，由此确定这些电流的比率（I-ratio）。利用i -比值评价温度依赖性使除渗透外的其他因素的影响降到最低。在较宽的温度范围内（4-49℃）应用不同程度的温度跳变（δ T， -15至15℃），并从I（比）s计算质子电流的Q(10)s。Q（10）表现出高温依赖性，从10℃时的2.2到40℃时的1.3，这意味着不同温度依赖性的过程是观察到的Q（10）的基础。一种新的电阻率脉冲法揭示了具有低温依赖性的接入电阻在高温范围内占主导地位。将测得的Q（10）与温度的关系分解为通道的Q（10）和接入电阻的Q（10）。最后，计算了质子通过电压门控质子通道本身的Q(10)，发现在5℃时从2.8变化到45℃时的2.2，正如预期的活化焓为64 kJ/mol。讨论了质子通过质子选择通道渗透的热力学特征，探讨了其潜在机理。
Voltage-gated proton channels are found in many different types of cells, where they facilitate proton movement through the membrane. The mechanism of proton permeation through the channel is an issue of long-term interest, but it remains an open question. To address this issue, we examined the temperature dependence of proton permeation. Under whole cell recordings, rapid temperature changes within a few milliseconds were imposed. This method allowed for the measurement of current amplitudes immediately before and after a temperature jump, from which the ratios of these currents (I-ratio) were determined. The use of I-ratio for evaluating the temperature dependence minimized the contributions of factors other than permeation. Temperature jumps of various degrees (Delta T, -15 to 15 degrees C) were applied over a wide temperature range (4-49 degrees C), and the Q(10)s for the proton currents were evaluated from the I(ratio)s. Q(10) exhibited a high temperature dependence, varying from 2.2 at 10 degrees C to 1.3 at 40 degrees C. This implies that processes with different temperature dependencies underlie the observed Q(10). A novel resistivity pulse method revealed that the access resistance with its low temperature dependence predominated in high temperature ranges. The measured temperature dependence of Q(10) was decomposed into Q(10) of the channel and of the access resistances. Finally, the Q(10) for proton permeation through the voltage-gated proton channel itself was calculated and found to vary from 2.8 at 5 degrees C to 2.2 at 45 degrees C, as expected for an activation enthalpy of 64 kJ/mol. The thermodynamic features for proton permeation through proton-selective channels were discussed for the underlying mechanism.