Merrill A R, Cramer W A
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
Biochemistry. 1990 Sep 18;29(37):8529-34. doi: 10.1021/bi00489a004.
The voltage dependence of channel activity of the bactericidal protein colicin E1 was found to be correlated with insertion into the membrane bilayer of a specific segment of the 178-residue COOH-terminal thermolytic colicin channel peptide. The insertion into the bilayer was detected by an increase in labeling by one of two different lipophilic photoaffinity probes or by a decrease in iodination of peptide tyrosines from the external solution. Imposition of a potassium diffusion potential of -100 mV resulted in an increase of 35-60% in the labeling of the peptide by the lipophilic probe in the bilayer and a concomitant decrease in labeling of Tyr residues in the peptide by the iodination reagent in the external solution. The change in labeling decreased upon dissipation of the membrane potential with a half-time of about 1 min. The labeling change was localized to a 36-residue peptide segment bounded by alanine-425 and by tryptophan-460. This segment containing seven positively charged residues at low pH is a voltage-sensitive region that inserts into the membrane bilayer when the channel is turned on by the potential and is extruded from it when the voltage is removed and the channel is turned off.
杀菌蛋白大肠杆菌素E1通道活性的电压依赖性被发现与178个氨基酸残基的COOH末端热解大肠杆菌素通道肽的特定片段插入膜双层相关。通过两种不同亲脂性光亲和探针之一标记的增加或通过外部溶液中肽酪氨酸碘化的减少来检测插入双层的情况。施加-100 mV的钾扩散电位导致双层中亲脂性探针标记肽增加35 - 60%，同时外部溶液中碘化试剂对肽中酪氨酸残基的标记减少。膜电位消散时，标记变化以约1分钟的半衰期下降。标记变化局限于由丙氨酸-425和色氨酸-460界定的36个氨基酸残基的肽段。该片段在低pH下含有七个带正电荷的残基，是一个电压敏感区域，当通道因电位而开启时插入膜双层，当电压去除且通道关闭时从膜双层中挤出。
