Rudy B, Hoger J H, Lester H A, Davidson N
Department of Physiology and Biophysics, NYU Medical Center, New York 10016.
Neuron. 1988 Oct;1(8):649-58. doi: 10.1016/0896-6273(88)90164-x.
Fast transient K+ channels (A channels) of the type operating in the subthreshold region for Na+ action potential generation were expressed in Xenopus oocytes injected with rat brain poly(A) RNA. Sucrose gradient fractionation of the RNA separates mRNAs encoding A-currents (6-7 kb) from mRNAs encoding other voltage-dependent K+ channels. A-currents expressed with fractionated mRNA differ in kinetics and pharmacology from A-currents expressed with total mRNA. The original properties of the A-currents can be reconstituted when small mRNAs (2-4 kb) are added to the large mRNA fraction. Thus the properties of the A-currents expressed with total poly(A) RNA depend on the presence of more than one mRNA species. mRNA(s) present in the large RNA fraction must encode channel subunits since they express an A-current by themselves. The small mRNA(s) may encode a second subunit(s) or a factor, such as an enzymatic activity that modulates the properties of the channels, which could play a role in generating A-channel functional diversity.
在产生钠动作电位的阈下区域发挥作用的快速瞬时钾离子通道（A通道），在注射了大鼠脑聚腺苷酸RNA的非洲爪蟾卵母细胞中得以表达。RNA的蔗糖梯度分级分离将编码A电流的mRNA（6 - 7 kb）与编码其他电压依赖性钾离子通道的mRNA区分开来。用分级分离的mRNA表达的A电流在动力学和药理学特性上与用总mRNA表达的A电流不同。当将小mRNA（2 - 4 kb）添加到大mRNA组分中时，A电流的原始特性可以得以重构。因此，用总聚腺苷酸RNA表达的A电流特性取决于不止一种mRNA种类的存在。大RNA组分中存在的mRNA必定编码通道亚基，因为它们自身就能表达A电流。小mRNA可能编码第二种亚基或一种因子，比如一种调节通道特性的酶活性，这可能在产生A通道功能多样性中发挥作用。
