Sato C, Matsumoto G
Electrotechnical Laboratory, Supermolecular Science Division, Ibaraki, Japan.
J Membr Biol. 1995 Sep;147(1):45-70. doi: 10.1007/BF00235397.
The complete amino acid sequence of a sodium channel from squid Loligo bleekeri has been deduced by cloning and sequence analysis of the complementary DNA. A unique feature of the squid sodium channel is the 1,522 residue sequence, approximately three-fourths of those of the rat sodium channels I, II and III. On the basis of the sequence, and in comparison with those of vertebrate sodium channels, we have proposed a tertiary structure model of the sodium channel where the transmembrane segments are octagonally aligned and the four linkers of S5-6 between segments S5 and S6 play a crucial role in the activation gate, voltage sensor and ion selective pore, which can slide, depending on membrane potentials, along inner walls consisting of alternating segments S2 and S4. The proposed octagonal structure model is contrasted with that of Noda et al. (Nature 320; 188-192, 1986). The octagonal structure model can explain the gating of activation and inactivation, and ion selectivity, as well as the action mechanism of both tetrodotoxin (TTX) and alpha-scorpion toxin (ScTX), and can be applied not only to the sodium channel, but also to the calcium channel, potassium channel and cGMP-gated channel.
通过对鱿鱼（Loligo bleekeri）钠通道互补DNA的克隆和序列分析，推导得出了其完整的氨基酸序列。鱿鱼钠通道的一个独特特征是其1522个残基的序列，约为大鼠钠通道I、II和III序列的四分之三。基于该序列，并与脊椎动物钠通道的序列进行比较，我们提出了钠通道的三级结构模型，其中跨膜片段呈八边形排列，S5和S6片段之间的四个S5-6连接子在激活门、电压传感器和离子选择性孔中起关键作用，它们可根据膜电位沿着由交替的S2和S4片段组成的内壁滑动。所提出的八边形结构模型与野田等人（《自然》320；188 - 192，1986）的模型形成对比。该八边形结构模型能够解释激活和失活的门控、离子选择性，以及河豚毒素（TTX）和α - 蝎毒素（ScTX）的作用机制，并且不仅可应用于钠通道，还可应用于钙通道、钾通道和cGMP门控通道。
