Constraints on voltage sensor movement in the shaker K+ channel.
Constraints on voltage sensor movement in the shaker K+ channel.
复制标题
振动弹器K+通道中电压传感器运动的限制。
DOI：
10.1085/jgp.200609624
复制
发表时间：
2006-12
影响因子：
3.8
通讯作者：
Blaustein, Robert O
中科院分区：
文献类型：
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作者：
Darman, Rachel B;Ivy, Allison A;Ketty, Vina;Blaustein, Robert O
在神经和肌肉细胞中，电压门控的阳离子选择性离子通道的开放和关闭伴随着12-14个基元电荷跨膜电场的转移。虽然大多数这些电荷是由这些通道的门控模块的S4螺旋中的残基携带的，但它们物理运动的确切性质目前是激烈辩论的话题。总的来说，已经出现了两类模型：一类认为小范围的运动可以解释大范围的电荷移动，另一类则引发了更大的物理运动。在后一类模型的最新化身中，基于来自考古菌K+通道Kvap的结构和功能数据，由S3-S4的螺旋-转弯螺旋组成的“电压传感器桨”在门控周期中通过双层移位∼20？(酱，Y.，A.Lee，J.Chen，V.Ruta，M.Cadene，B.T.Chait和R.MacKinnon)。2003年。大自然。423：33-41；姜，Y.，V.Ruta，J.Chen，A.Lee和R.MacKinnon。2003年。大自然。423：42-48；Ruta，V.，J.Chen和R.MacKinnon。2005年。牢房。123：463-475)。我们使用了两种方法来测试Shaker K+通道中的类似运动，每种方法都检查了S3附近残基的水溶液暴露情况。在第一个实验中，我们使用了一种堵孔的马来酰亚胺试剂(Blaustein，R.O.，P.A.Cole，C.Williams和C.Miller)。2000年。纳特。结构。比奥尔。7：309-311)，以探索取代半胱氨酸的化学反应活性的状态依赖变化；在第二个实验中，我们测试了拴系生物素与外部链霉亲和素(Chu，X.Q，K.S.Jake，A.Finkelstein和S.L.Slatin)的状态依赖可及性。1994年。J.Biol.化学。269：7483-7488；Slatin，S.L.，X.Q.邱，K.S.Jkers，A.Finkelstein。1994年。大自然。371：158-161)。在这两种类型的实验中，预测位于S3顶部附近的残留物在选通周期期间没有表现出任何水暴露的变化。这种状态依赖性的缺乏与Shaker的S3-S4电压传感器桨的轴向或径向大规模运动相抵触。
In nerve and muscle cells, the voltage-gated opening and closing of cation-selective ion channels is accompanied by the translocation of 12–14 elementary charges across the membrane's electric field. Although most of these charges are carried by residues in the S4 helix of the gating module of these channels, the precise nature of their physical movement is currently the topic of spirited debate. Broadly speaking, two classes of models have emerged: those that suggest that small-scale motions can account for the extensive charge displacement, and those that invoke a much larger physical movement. In the most recent incarnation of the latter type of model, which is based on structural and functional data from the archaebacterial K+ channel KvAP, a “voltage-sensor paddle” comprising a helix-turn-helix of S3–S4 translocates ∼20 Å through the bilayer during the gating cycle (Jiang, Y., A. Lee, J. Chen, V. Ruta, M. Cadene, B.T. Chait, and R. MacKinnon. 2003. Nature. 423:33–41; Jiang, Y., V. Ruta, J. Chen, A. Lee, and R. MacKinnon. 2003. Nature. 423:42–48.; Ruta, V., J. Chen, and R. MacKinnon. 2005. Cell. 123:463–475). We used two methods to test for analogous motions in the Shaker K+ channel, each examining the aqueous exposure of residues near S3. In the first, we employed a pore-blocking maleimide reagent (Blaustein, R.O., P.A. Cole, C. Williams, and C. Miller. 2000. Nat. Struct. Biol. 7:309–311) to probe for state-dependent changes in the chemical reactivity of substituted cysteines; in the second, we tested the state-dependent accessibility of a tethered biotin to external streptavidin (Qiu, X.Q., K.S. Jakes, A. Finkelstein, and S.L. Slatin. 1994. J. Biol. Chem. 269:7483–7488; Slatin, S.L., X.Q. Qiu, K.S. Jakes, and A. Finkelstein. 1994. Nature. 371:158–161). In both types of experiments, residues predicted to lie near the top of S3 did not exhibit any change in aqueous exposure during the gating cycle. This lack of state dependence argues against large-scale movements, either axially or radially, of Shaker's S3–S4 voltage-sensor paddle.