Role of charged residues in the S1-S4 voltage sensor of BK channels.
Role of charged residues in the S1-S4 voltage sensor of BK channels.
复制标题
DOI：
10.1085/jgp.200509421
复制
发表时间：
2006-03
期刊：
影响因子：
--
通讯作者：
Horrigan FT
中科院分区：
文献类型：
--
作者：
Ma Z;Lou XJ;Horrigan FT
与Shaker和其他电压门控K+(KV)通道相比，大电导钙激活(BK)钾通道的激活具有较弱的电压依赖性。然而，BK和KV通道在跨膜片段S1-S4中共享许多保守的带电残基。我们在mSlo1BK通道中分别突变这些残基以确定它们在电压门控中的作用，并在0-50μM[Ca+]i的扩展电压范围内表征了稳态激活(Po)和IK动力学(Ik)的电压依赖性。mSlo1在S4中含有几个带正电荷的精氨酸，但只有一个(R213)以及S2(D153，R167)和S3(D186)中的残基是潜在的电压敏感，这是基于电荷改变突变降低PO的最大电压依赖性的能力。PO和τ(Ik)在极负电位下的电压依赖性也降低了，这意味着闭合-开合构象变化和电压传感器的激活共享一个共同的门控电荷来源。尽管带电残基在BK和KV通道序列中的位置似乎是保守的，但电压敏感残基的分布却不是这样。因此，BK通道激活的弱电压依赖性不仅反映了电荷的缺乏，而且可能反映了带电残基在电场中的位置和运动方面与KV通道的差异。虽然S1-S4中大多数位点的突变并没有减少门控电荷，但它们经常改变电压传感器激活的平衡常数。特别是，R207或R210在S4中的中和使活化状态稳定了3-7kcal−1，表明非电压敏感残基对通道功能的贡献很大，这与它们参与状态依赖的盐桥相互作用是一致的。S4和S3(R210E、D186A和E180A)的突变也意外地削弱了电压传感器激活与通道开放的变构耦合。我们的发现对BK通道电压门控和电压传感器激活的一般机制的影响进行了讨论。
The activation of large conductance Ca2+-activated (BK) potassium channels is weakly voltage dependent compared to Shaker and other voltage-gated K+ (KV) channels. Yet BK and KV channels share many conserved charged residues in transmembrane segments S1–S4. We mutated these residues individually in mSlo1 BK channels to determine their role in voltage gating, and characterized the voltage dependence of steady-state activation (Po) and IK kinetics (τ(IK)) over an extended voltage range in 0–50 μM [Ca2+]i. mSlo1 contains several positively charged arginines in S4, but only one (R213) together with residues in S2 (D153, R167) and S3 (D186) are potentially voltage sensing based on the ability of charge-altering mutations to reduce the maximal voltage dependence of PO. The voltage dependence of PO and τ(IK) at extreme negative potentials was also reduced, implying that the closed–open conformational change and voltage sensor activation share a common source of gating charge. Although the position of charged residues in the BK and KV channel sequence appears conserved, the distribution of voltage-sensing residues is not. Thus the weak voltage dependence of BK channel activation does not merely reflect a lack of charge but likely differences with respect to KV channels in the position and movement of charged residues within the electric field. Although mutation of most sites in S1–S4 did not reduce gating charge, they often altered the equilibrium constant for voltage sensor activation. In particular, neutralization of R207 or R210 in S4 stabilizes the activated state by 3–7 kcal mol−1, indicating a strong contribution of non–voltage-sensing residues to channel function, consistent with their participation in state-dependent salt bridge interactions. Mutations in S4 and S3 (R210E, D186A, and E180A) also unexpectedly weakened the allosteric coupling of voltage sensor activation to channel opening. The implications of our findings for BK channel voltage gating and general mechanisms of voltage sensor activation are discussed.
登录
查看更多内容
影响因子：
16.2
作者：
Aggarwal, SK;MacKinnon, R
通讯作者：
MacKinnon, R
影响因子：
16.2
作者：
Larsson, HP;Baker, OS;Isacoff, EY
通讯作者：
Isacoff, EY
内部BA2+与平滑肌的克隆Ca（2+） - 依赖性K+（HSLO）通道的相互作用。
影响因子：
3.8
作者：
Diaz, F;Wallner, M;Stefani, E;Toro, L;Latorre, R
通讯作者：
Latorre, R
影响因子：
3.8
作者：
Ledwell, JL;Aldrich, RW
通讯作者：
Aldrich, RW
需要十二个电荷的转移以打开骨骼肌Na+通道。
影响因子：
3.8
作者：
Hirschberg, B;Rovner, A;Lieberman, M;Patlak, J
通讯作者：
Patlak, J