Spires S, Begenisich T
Department of Physiology, University of Rochester Medical Center, New York 14642-8642.
J Gen Physiol. 1992 Jan;99(1):109-29. doi: 10.1085/jgp.99.1.109.
We have examined the actions of several amino group reagents on delayed rectifier potassium channels in squid giant axons. Three general classes of reagents were used: (1) those that preserved the positive charge of amino groups; (2) those that neutralize the charge; and (3) those that replace the positive with a negative charge. All three types of reagents produced qualitatively similar effects on K channel properties. Trinitrobenzene sulfonic acid (TNBS) neutralizes the peptide terminal amino groups and the epsilon-amino group of lysine groups. TNBS (a) slowed the kinetics of macroscopic ionic currents; (b) increased the size of ionic currents at large positive voltages; (c) shifted the voltage-dependent probability of channel opening to more positive potentials but had no effect on the voltage sensitivity; and (d) altered several properties of K channel gating currents. The actions of TNBS on gating currents suggest the presence of multiple gating current components. These effects are not all coupled, suggesting that several amino groups on the external surface of K channels are important for channel gating. A simple kinetic model that considers the channel to be composed of independent heterologous subunits is consistent with most of the modifications produced by amino group reagents.
我们研究了几种氨基试剂对鱿鱼巨轴突延迟整流钾通道的作用。使用了三类试剂：（1）保留氨基正电荷的试剂；（2）中和电荷的试剂；（3）用负电荷取代正电荷的试剂。这三种类型的试剂对钾通道特性产生了定性相似的影响。三硝基苯磺酸（TNBS）中和肽末端氨基和赖氨酸基团的ε-氨基。TNBS（a）减慢了宏观离子电流的动力学；（b）在大的正电压下增加了离子电流的大小；（c）将通道开放的电压依赖性概率向更正的电位移动，但对电压敏感性没有影响；（d）改变了钾通道门控电流的几个特性。TNBS对门控电流的作用表明存在多个门控电流成分。这些效应并非都相互关联，这表明钾通道外表面的几个氨基对通道门控很重要。一个简单的动力学模型，认为通道由独立的异源亚基组成，与氨基试剂产生的大多数修饰是一致的。
