Boland L M, Jurman M E, Yellen G
Department of Neurobiology, Massachusetts General Hospital, Boston 02114.
Biophys J. 1994 Mar;66(3 Pt 1):694-9. doi: 10.1016/s0006-3495(94)80843-4.
We investigated whether the cysteine residues in Shaker potassium (K+) channels are essential for activation and inactivation gating or for modulation of activation gating by external zinc (Zn2+). Mutants of the Shaker K+ channel were prepared in which all seven cysteine residues were replaced (C-less). These changes were made in both wild-type Shaker H4 channels and in a deletion mutant (delta 6-46) lacking N-type ("fast") inactivation. Replacement of all cysteines left most functional properties of the K+ currents unaltered. The most noticeable difference between the C-less and wild-type currents was the faster C-type inactivation of the C-less channel which could be attributed largely to the mutation of Cys462. This is consistent with the effects of previously reported mutations of nearby residues in the S6 region. There were also small changes in the activation gating of C-less currents. Modulation by external Zn2+ of the voltage dependence and rate of activation gating is preserved in the C-less channels, indicating that none of the cysteines in the Shaker K+ channel plays an important role in Zn2+ modulation.
我们研究了Shaker钾（K+）通道中的半胱氨酸残基对于激活和失活门控，或对于外部锌（Zn2+）对激活门控的调节是否至关重要。制备了Shaker K+通道的突变体，其中所有七个半胱氨酸残基均被替换（无半胱氨酸）。在野生型Shaker H4通道和缺乏N型（“快速”）失活的缺失突变体（δ6-46）中都进行了这些改变。所有半胱氨酸的替换使K+电流的大多数功能特性保持不变。无半胱氨酸电流与野生型电流之间最明显的差异是无半胱氨酸通道的C型失活更快，这在很大程度上可归因于Cys462的突变。这与先前报道的S6区域附近残基突变的效应一致。无半胱氨酸电流的激活门控也有小变化。外部Zn2+对电压依赖性和激活门控速率的调节在无半胱氨酸通道中得以保留，表明Shaker K+通道中的半胱氨酸均未在Zn2+调节中起重要作用。
