The pore, not cytoplasmic domains, underlies inactivation in a prokaryotic sodium channel
The pore, not cytoplasmic domains, underlies inactivation in a prokaryotic sodium channel
复制标题
DOI：
10.1529/biophysj.104.056994
复制
发表时间：
2005-07-01
影响因子：
3.4
通讯作者：
French, RJ
中科院分区：
文献类型：
--
作者：
Pavlov, E;Bladen, C;French, RJ
研究了原核电压门控钠通道 (NaChBac) 失活的动力学和电压依赖性，以了解其分子机制。 NaChBac 失活动力学表现出强烈的钟形电压依赖性，其特征时间常数范围从去极化电压下的大约 50 毫秒到失活中点处的最大大约 100 秒。四种不同的共价连接串联二聚体或串联四聚体构建体的激活和失活参数与野生型通道的激活和失活参数没有区别。孔外部的点突变揭示了S195残基对失活过程的重要影响。对于两种突变体（S195D 和 S195E），与野生型通道相比，观察到的最大和最小失活率增加了约 2.5 倍，并且稳态失活曲线的中点在超极化方向上移动了约 20 mV。我们的数据表明，孔前庭结构是 NaChBac 失活的重要决定因素，而失活机制与功能通道中游离细胞质 N 端和 C 端的数量无关。在这些方面，NaChBac 失活类似于在其他电压门控 K 和 Na 通道中观察到的 C 型或缓慢失活模式。
Kinetics and voltage dependence of inactivation of a prokaryotic voltage-gated sodium channel (NaChBac) were investigated in an effort to understand its molecular mechanism. NaChBac inactivation kinetics show strong, bell-shaped voltage dependence with characteristic time constants ranging from similar to 50 ms at depolarized voltages to a maximum of similar to 100 s at the inactivation midpoint. Activation and inactivation parameters for four different covalently linked tandem dimer or tandem tetramer constructs were indistinguishable from those of the wild-type channel. Point mutations in the outer part of the pore revealed an important influence of the S195 residue on the process of inactivation. For two mutants (S195D and S195E), the maximal and minimal rates of inactivation observed were increased by similar to 2.5-fold, and the midpoint of the steady-state inactivation curve was shifted similar to 20 mV in the hyperpolarizing direction, compared to the wild-type channel. Our data suggest that pore vestibule structure is an important determinant of NaChBac inactivation, whereas the inactivation mechanism is independent of the number of free cytoplasmic N- and C-termini in the functional channel. In these respects, NaChBac inactivation resembles C-type or slow inactivation modes observed in other voltage-gated K and Na channels.