Research on inactivation of the hybrid K channel.

我们以前报道过，在Kv1.4/Kv1.2混合通道中观察到的电流与同源四聚体Kv1.4通道非常相似，在去极化脉冲期间显示快速失活。已阐明在杂交通道中，非失活亚基Kv1.2的S4-S5胞内环可能是Kv1.4亚基失活门的受体部分。该项目的目的是研究组成型亚基对电流失活的相对贡献。研究了Kv1.4或Kv1.2的S4-S5环中的点突变对杂交通道失活的影响。Kv1.4的S4-S5环和Kv1.2的相应氨基酸的突变对失活时间常数具有相似的影响，这表明来自每个组成亚基的所有S4-S5环作为失活门的受体同等地贡献于失活。将Kv1.4或Kv1.2的S5-S6区域替换为Kv1.2或Kv1.4的相应区域，或将两个组分之间的S5-S6区域互换，构建编码杂交通道的融合基因。所有这些混合通道的失活特征是相似的。从这些结果表明，所有组成亚基的S5-S6区同样有助于电流的失活。

We previously reported that the current observed in Kv1.4/Kv1.2 hybrid channel is very similar to that of the homotetrameric Kv1.4 channel ; which shows rapid inactivation during depolarizing pulses. It has been elucidated that in the hybrid channel the S4-S5 intracellular loop of non-inactivating subunit Kv1.2 could be part of the acceptor for the inactivation gates thetered from Kv1.4 subunit. This project was planned in order to investigate the relative contribution of the constitutive subunits to inactivation of the currents. The effects of a point mutation in the S4-S5 loop of Kv1.4 or Kv1.2 on inactivation of the hybrid channel were examined. Mutations in the S4-S5 loop of Kv1.4 and the corresponding amino acid of Kv1.2 had similar effects on inactivation time constant, suggesting that all of the S4-S5 loops derived from each constituent subunit equally contribute to inactivation as the acceptor for the inactivation gates.The role of the S5-S6 regions of Kv1.4 and Kv1.2 subunits in inactivation was also examined. The fusion genes encoding the hybrid channels were constructed, in which S5-S6 region of Kv1.4 or Kv1.2 was replaced with the corresponding region of Kv1.2 or Kv1.4, or the S5-S6 regions were interchanged between the two components. Characteristics of inactivation for all of these hybrid channels were similar. It was suggested from these results that the S5-S6 regions of all constituent subunits equally contribute to inactivation of the currents.