Lopatin A N, Makhina E N, Nichols C G
Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110.
Nature. 1994 Nov 24;372(6504):366-9. doi: 10.1038/372366a0.
Inwardly rectifying potassium channels conduct ions more readily in the inward than the outward direction, an essential property for normal electrical activity. Although voltage-dependent block by internal magnesium ions may underlie inward rectification in some channels, an intrinsic voltage-dependent closure of the channel plays a contributory, or even exclusive, role in others. Here we report that, rather than being intrinsic to the channel protein, so-called intrinsic rectification of strong inward rectifiers requires soluble factors that are not Mg2+ and can be released from Xenopus oocytes and other cells. Biochemical and biophysical characterization identifies these factors as polyamines (spermine, spermidine, putrescine and cadaverine). The results suggest that intrinsic rectification results from voltage-dependent block of the channel pore by polyamines, not from a voltage sensor intrinsic to the channel protein.
内向整流钾通道在向内方向比向外方向更容易传导离子，这是正常电活动的一个基本特性。尽管内部镁离子的电压依赖性阻断可能是某些通道内向整流的基础，但通道的固有电压依赖性关闭在其他通道中起了促成甚至是唯一的作用。在这里我们报告，所谓的强内向整流器的固有整流并非通道蛋白所固有，而是需要可溶因子，这些因子不是Mg2+，并且可以从非洲爪蟾卵母细胞和其他细胞中释放出来。生化和生物物理特性鉴定表明这些因子是多胺（精胺、亚精胺、腐胺和尸胺）。结果表明，固有整流是由多胺对通道孔的电压依赖性阻断引起的，而不是由通道蛋白固有的电压传感器引起的。
