Anion pathway and potential energy profiles along curvilinear bacterial ClC Cl- pores: electrostatic effects of charged residues.
Anion pathway and potential energy profiles along curvilinear bacterial ClC Cl- pores: electrostatic effects of charged residues.
复制标题
沿曲线细菌 ClC Cl- 孔的阴离子路径和势能分布：带电残留物的静电效应。
DOI：
10.1016/s0006-3495(04)74158-2
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发表时间：
2004
影响因子：
3.4
通讯作者：
Jordan,PeterC
中科院分区：
文献类型：
--
作者：
Miloshevsky,GennadyV;Jordan,PeterC
X射线结构允许从理论上研究氯离子−沿细菌ClC氯离子−孔道的渗透。我们确定了最低能量曲线路径，确定了与阴离子配位的氨基酸，并计算了静电势能分布。我们发现，四种细菌ClC、Cl、−的晶体结构都对应于闭合状态。在StClC野生型和EcClC野生型晶体中，E148和S107侧链在晶体结合部位两侧形成空间位阻；EcClC(E148A)和EcClC(E148Q)突变体都被阻断在S107位点。我们研究了一些强守恒的孔衬氨基酸的电荷突变对静电势能分布的影响。当E148被中和时，它会产生一个静电陷阱，将离子结合在中膜附近。这提示了一种可能的控制阴离子流动的静电机制：中和E148，将E148的侧链从孔道上移位以解除空间位阻，然后将阴离子捕获到中膜，最后去质子化E148并堵塞孔(孔闭合)或将第二个Cl−带入孔中以促进阴离子流(孔电导)。侧链位移可能是由于E148的氧基团与沿着静电能量梯度向下移动的阴离子之间竞争结合部位而引起的。我们还发现，E111和E113的电荷态可能通过静电作用控制着阴离子电导和结合位在胞质孔内的占有率。
X-ray structures permit theoretical study of Cl−permeation along bacterial ClC Cl−pores. We determined the lowest energy curvilinear pathway, identified anion-coordinating amino acids, and calculated the electrostatic potential energy profiles. We find that all four bacterial ClC Cl−crystal structures correspond to closed states. E148 and S107 side chains form steric barriers on both sides of the crystal binding site in the StClC wild-type and EcClC wild-type crystals; both the EcClC(E148A) and EcClC(E148Q) mutants are blocked at the S107 site. We studied the effect that mutating the charge of some strongly conserved pore-lining amino acids has on the electrostatic potential energy profiles. When E148 is neutralized, it creates an electrostatic trap, binding the ion near midmembrane. This suggests a possible electrostatic mechanism for controlling anion flow: neutralize E148, displace the side chain of E148 from the pore pathway to relieve the steric barrier, then trap the anion at midmembrane, and finally either deprotonate E148 and block the pore (pore closure) or bring a second Cl−into the pore to promote anion flow (pore conductance). Side-chain displacement may arise by competition for the binding site between the oxygens of E148 and the anion moving down the electrostatic energy gradient. We also find that the charge state of E111 and E113 may electrostatically control anion conductance and occupancy of the binding site within the cytoplasmic pore.