Role of the central arginine R133 toward the ion selectivity of the phosphate specific channel OprP: effects of charge and solvation.
Role of the central arginine R133 toward the ion selectivity of the phosphate specific channel OprP: effects of charge and solvation.
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DOI：
10.1021/bi400522b
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发表时间：
2013-08
期刊：
影响因子：
2.9
通讯作者：
Niraj Modi;Iván Bárcena-Uribarri;M. Bains;R. Benz;R. Hancock;U. Kleinekathöfer
中科院分区：
文献类型：
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作者：
Niraj Modi;Iván Bárcena-Uribarri;M. Bains;R. Benz;R. Hancock;U. Kleinekathöfer
铜绿假单胞菌的外膜孔蛋白OprP形成高度特异性的磷酸盐选择性通道。该通道负责将磷酸盐离子高亲和力摄取到细菌的周质空间中。为了破译该孔蛋白的阴离子和磷酸盐选择性，并拓宽目前对不同通道离子选择性的理解，对OprP结构-功能关系的详细研究是不可避免的。为此，我们研究了 OprP 的中心精氨酸 R133 对孔的选择性和离子传输特性的影响。进行了电生理学双层测量和自由能分子动力学模拟，以探测不同离子通过各种 R133 突变体的运输。对于这些突变体，确定了磷酸盐结合特异性、离子传导和阴离子选择性的变化，并与之前使用野生型 OprP 进行的分子动力学计算和电生理学测量进行了比较。分子分析揭示了精氨酸133及其电荷的相当特殊的作用，同时该残基与其他残基网络（即D94和Y114）一起具有使渗透离子脱水的能力。这些非常具体的特征决定了 OprP 的离子选择性。
The outer membrane porin OprP of Pseudomonas aeruginosa forms a highly specific phosphate selective channel. This channel is responsible for the high-affinity uptake of phosphate ions into the periplasmic space of the bacteria. A detailed investigation of the structure-function relationship of OprP is inevitable to decipher the anion and phosphate selectivity of this porin in particular and to broaden the present understanding of the ion selectivity of different channels. To this end we investigated the role of the central arginine of OprP, R133, in terms of its effects in selectivity and ion transport properties of the pore. Electrophysiological bilayer measurements and free-energy molecular dynamics simulations were carried out to probe the transport of different ions through various R133 mutants. For these mutants, the change in phosphate binding specificity, ion conduction, and anion selectivity was determined and compared to previous molecular dynamic calculations and electrophysiological measurements with wild-type OprP. Molecular analysis revealed a rather particular role of arginine 133 and its charge, while at the same time this residue together with the network of other residues, namely, D94 and Y114, has the ability to dehydrate the permeating ion. These very specific features govern the ion selectivity of OprP.