The role of Trp side chains in tuning single proton conduction through gramicidin channels
The role of Trp side chains in tuning single proton conduction through gramicidin channels
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DOI：
10.1016/s0006-3495(02)75215-6
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发表时间：
2002-08-01
影响因子：
3.4
通讯作者：
Schumaker, MF
中科院分区：
文献类型：
--
作者：
Gowen, JA;Markham, JC;Schumaker, MF
我们提出了一套广泛的质子传导测量，通过gramicidin A (gA), B （gB）和M （gM）同型二聚体通道，在通道的每一端分别有4,3或0个Trp残基。在gA中，我们发现一个肩部将两个电导率随浓度增加的域分开，证实了Eisenman， G.， B. Enos， J. Hagglunc和J. Sandblom. 1980的结果。安。纽约。科学学报，339:8-20。在gB中，肩向更高的H+浓度移动了大约1/2个pH单位，并且非常明确。在gM数据中没有出现肩带，但在gM数据中，从亚线性到超线性的I-V值的相关转变发生在[H+]比gA高100倍的地方。使用单质子传导的构型空间模型分析低浓度域的数据，假设gA和其类似物之间的平均力的质子势（PMF）的差异是恒定的，类似于Anderson， D.， R. B. Shirts， T. a . Cross和D. D. Busath, 2001， Biophys的结果。j . 81:1255 - 1264。我们的研究结果表明，计算出的质子PMFs的平均振幅几乎是正确的，但是通过分子动力学使用PM6水模型计算出的gA的水重定向势垒（Pomes， R., and B. Roux. 1997）。Biophys。J. 72:246a)的振幅必须降低1.5 kcal/mol或更多，并且对gA没有速率限制。
We present an extensive set of measurements of proton conduction through gramicidin A (gA), B (gB), and M (gM) homodimer channels which have 4, 3, or 0 Trp residues at each end of the channel, respectively. In gA we find a shoulder separating two domains of conductance increasing with concentration, confirming the results of Eisenman, G., B. Enos, J. Hagglunc, and J. Sandblom. 1980. Ann. NY. Acad. Sci. 339:8-20. In gB, the shoulder is shifted by similar to1/2 pH unit to higher H+ concentrations and is very sharply defined. No shoulder appears in the gM data, but an associated transition from sublinear to superlinear I-V values occurs at a 100-fold higher [H+] in gM than in gA. The data in the low concentration domain are analyzed using a configuration space model of single-proton conduction, assuming that the difference in the proton potential of mean force (PMF) between gA and its analogs is constant, similar to the results of Anderson, D., R. B. Shirts, T. A. Cross, and D. D. Busath. 2001, Biophys. J. 81:1255-1264. Our results suggest that the average amplitudes of the calculated proton PMFs are nearly correct, but that the water reorientation barrier calculated for gA by molecular dynamics using the PM6 water model (Pomes, R., and B. Roux. 1997. Biophys. J. 72:246a) must be reduced in amplitude by 1.5 kcal/mol or more, and is not rate-limiting for gA.