MacKinnon R, Miller C
Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02254.
Science. 1989 Sep 22;245(4924):1382-5. doi: 10.1126/science.2476850.
The inhibition by charybdotoxin of A-type potassium channels expressed in Xenopus oocytes was studied for several splicing variants of the Drosophila Shaker gene and for several site-directed mutants of this channel. Charybdotoxin blocking affinity is lowered by a factor of 3.5 upon replacing glutamate-422 with glutamine, and by a factor of about 12 upon substituting lysine in this position. Replacement of glutamate-422 by aspartate had no effect on toxin affinity. Thus, the glutamate residue at position 422 of this potassium channel is near or in the externally facing mouth of the potassium conduction pathway, and the positively charged toxin is electrostatically focused toward its blocking site by the negative potential set up by glutamate-422.
针对果蝇震颤基因的几种剪接变体以及该通道的几种定点突变体，研究了非洲爪蟾卵母细胞中表达的A型钾通道受查卡毒素的抑制情况。将谷氨酸-422替换为谷氨酰胺后，查卡毒素的阻断亲和力降低了3.5倍，而在该位置替换赖氨酸后，阻断亲和力降低了约12倍。将谷氨酸-422替换为天冬氨酸对毒素亲和力没有影响。因此，该钾通道422位的谷氨酸残基靠近或位于钾传导途径面向外部的口部，带正电荷的毒素通过谷氨酸-422产生的负电位被静电聚焦到其阻断位点。
