Charge delocalization in proton channels, I: The aquaporin channels and proton blockage
Charge delocalization in proton channels, I: The aquaporin channels and proton blockage
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DOI：
10.1529/biophysj.106.091934
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发表时间：
2007-01-01
影响因子：
3.4
通讯作者：
Voth, Gregory A.
中科院分区：
文献类型：
--
作者：
Chen, Hanning;Ilan, Boaz;Voth, Gregory A.
利用精确的全原子分子动力学计算机模拟模型，研究了水通道中超额质子的离域性质对自由能垒和质子电导的显式贡献。特别地，计算并比较了离域(完全格罗休斯穿梭)质子和经典(非穿梭)离子沿两个水通道AQp1和GlpF的通道渗透自由能分布。为了阐明被认为是由两个α螺旋巨偶极子产生的双极场对质子阻塞的影响，还计算了两个通道的计算突变体的自由能分布，其中通过人为地释放主干原子来消除双极场。对质子和氢离子自由能分布的比较表明，完全离域和穿梭质子的自由能垒的大小和势垒峰的位置与(局域)经典氢离子的情况有所不同。用Poisson-Nernst-Planck理论计算了格洛特劳斯穿梭超额质子和经典离子的质子电导。
The explicit contribution to the free energy barrier and proton conductance from the delocalized nature of the excess proton is examined in aquaporin channels using an accurate all-atom molecular dynamics computer simulation model. In particular, the channel permeation free energy profiles are calculated and compared for both a delocalized (fully Grotthuss shuttling) proton and a classical (nonshuttling) hydronium ion along two aquaporin channels, Aqp1 and GlpF. To elucidate the effects of the bipolar field thought to arise from two alpha-helical macrodipoles on proton blockage, free energy profiles were also calculated for computational mutants of the two channels where the bipolar field was eliminated by artificially discharging the backbone atoms. Comparison of the free energy profiles between the proton and hydronium cases indicates that the magnitude of the free energy barrier and position of the barrier peak for the fully delocalized and shuttling proton are somewhat different from the case of the (localized) classical hydronium. The proton conductance through the two aquaporin channels is also estimated using Poisson-Nernst-Planck theory for both the Grotthuss shuttling excess proton and the classical hydronium cation.