钠通道的单点突变会在不影响其门控功能的情况下大幅降低孔道通透性。

Single point mutations of the sodium channel drastically reduce the pore permeability without preventing its gating.

Pusch M, Noda M, Stühmer W, Numa S, Conti F

Istituto di Cibernetica e Biofisica, CNR, Genova, Italy.

Eur Biophys J. 1991;20(3):127-33. doi: 10.1007/BF01561134.

Abstract

Two mutants of the sodium channel II have been expressed in Xenopus oocytes and have been investigated using the patch-clamp technique. In mutant E387Q the glutamic acid at position 387 has been replaced by glutamine, and in mutant D384N the aspartic acid at position 384 has been replaced by asparagine. 2. Mutant E387Q, previously shown to be resistant to block by tetrodotoxin (Noda et al. 1989), has a single-channel conductance of 4 pS, that can be easily measured only using noise analysis. At variance with the wild-type, the open-channel current-voltage relationship of mutant E387Q is linear over a wide voltage range even under asymmetrical ionic conditions. 3. Mutant D384N has a very low permeability for any of the following ions: Cl-, Na+, K+, Li+, Rb+, Ca2+, Mg2+, NH+4, TMA+, TEA+. However, asymmetric charge movements similar to the gating currents of the Na(+)-selective wild-type are still observed. 4. These results suggest that residues E387 and D384 interact directly with the pathway of the ions permeating the open channel.

摘要

钠通道II的两种突变体已在非洲爪蟾卵母细胞中表达，并使用膜片钳技术进行了研究。在突变体E387Q中，第387位的谷氨酸被谷氨酰胺取代；在突变体D384N中，第384位的天冬氨酸被天冬酰胺取代。2. 突变体E387Q先前已被证明对河豚毒素具有抗性（野田等，1989），其单通道电导为4 pS，仅使用噪声分析才能轻松测量。与野生型不同，即使在不对称离子条件下，突变体E387Q的开放通道电流-电压关系在很宽的电压范围内也是线性的。3. 突变体D384N对以下任何一种离子的通透性都非常低：Cl-、Na+、K+、Li+、Rb+、Ca2+、Mg2+、NH4+、TMA+、TEA+。然而，仍然观察到与Na(+)-选择性野生型的门控电流类似的不对称电荷移动。4. 这些结果表明，残基E387和D384与开放通道中离子渗透的途径直接相互作用。