del Camino D, Holmgren M, Liu Y, Yellen G
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Nature. 2000 Jan 20;403(6767):321-5. doi: 10.1038/35002099.
The structure of the bacterial potassium channel KcsA has provided a framework for understanding the related voltage-gated potassium channels (Kv channels) that are used for signalling in neurons. Opening and closing of these Kv channels (gating) occurs at the intracellular entrance to the pore, and this is also the site at which many open channel blockers affect Kv channels. To learn more about the sites of blocker binding and about the structure of the open Kv channel, we investigated here the ability of blockers to protect against chemical modification of cysteines introduced at sites in transmembrane segment S6, which contributes to the intracellular entrance. Within the intracellular half of S6 we found an abrupt cessation of protection for both large and small blockers that is inconsistent with the narrow 'inner pore' seen in the KcsA structure. These and other results are most readily explained by supposing that the structure of Kv channels differs from that of the non-voltage-gated bacterial channel by the introduction of a sharp bend in the inner (S6) helices. This bend would occur at a Pro-X-Pro sequence that is highly conserved in Kv channels, near the site of activation gating.
细菌钾通道KcsA的结构为理解用于神经元信号传导的相关电压门控钾通道（Kv通道）提供了一个框架。这些Kv通道的开启和关闭（门控）发生在孔道的细胞内入口处，这也是许多开放通道阻滞剂影响Kv通道的位点。为了更多地了解阻滞剂的结合位点以及开放Kv通道的结构，我们在此研究了阻滞剂保护跨膜片段S6中引入的半胱氨酸免受化学修饰的能力，S6对细胞内入口有贡献。在S6的细胞内一半区域，我们发现大小阻滞剂的保护作用都突然停止，这与KcsA结构中看到的狭窄“内孔”不一致。通过假设Kv通道的结构与非电压门控细菌通道的结构不同，即在内侧（S6）螺旋中引入了一个急剧弯曲，这些结果和其他结果最容易得到解释。这种弯曲将发生在Kv通道中高度保守的Pro-X-Pro序列处，靠近激活门控位点。
