Pak M D, Covarrubias M, Ratcliffe A, Salkoff L
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.
J Neurosci. 1991 Mar;11(3):869-80. doi: 10.1523/JNEUROSCI.11-03-00869.1991.
We have cloned and expressed a mouse brain K+ channel that is the homolog of the Drosophila Shab K+ channel. Mouse and Drosophila Shab K+ channels (mShab and fShab, respectively) represent an instance of K+ channels and structurally related species that are both functionally and structurally conserved; most kinetic, voltage-sensitive, and pharmacological properties are similar for the 2 channels. The greatest functional difference between the currents is recovery from inactivation, which is several times slower for mShab than for fShab currents. In addition to conserved structure, the mShab polypeptide has an unusually long nonconserved region at the carboxyl end of the protein. Truncation of 293 residues from the carboxyl end produced no noticeable change in voltage-sensitive, kinetic, or pharmacological properties. Thus, the measured functional properties of mShab are determined by the remaining 564 residues, most of which are conserved. The mShab and fShab channels are naturally occurring structural variants having substitutions in conserved portions that appear relatively neutral with respect to all measured properties except for, possibly, the rate of recovery from inactivation. The mShab current closely resembles a native delayed-rectifier-type potassium current, IK, in hippocampal neurons.
我们已经克隆并表达了一种小鼠脑钾离子通道，它是果蝇Shab钾离子通道的同源物。小鼠和果蝇的Shab钾离子通道（分别为mShab和fShab）代表了钾离子通道及其结构相关物种的一个实例，它们在功能和结构上都是保守的；这两种通道的大多数动力学、电压敏感性和药理学特性都相似。两种电流之间最大的功能差异在于失活后的恢复，mShab电流的恢复速度比fShab电流慢几倍。除了保守结构外，mShab多肽在蛋白质的羧基末端有一个异常长的非保守区域。从羧基末端截去293个残基后，电压敏感性、动力学或药理学特性没有明显变化。因此，mShab的实测功能特性由其余564个残基决定，其中大部分是保守的。mShab和fShab通道是天然存在的结构变体，在保守部分存在取代，除了失活后的恢复速率可能外，这些取代相对于所有实测特性似乎是相对中性的。mShab电流与海马神经元中的一种天然延迟整流型钾电流IK非常相似。
