Alekseev A E, Kennedy M E, Navarro B, Terzic A
Division of Cardiovascular Diseases, Guggenheim 7F, Mayo Clinic, Mayo Foundation, Rochester, MN 55905, USA.
J Membr Biol. 1997 Sep 15;159(2):161-8. doi: 10.1007/s002329900279.
Co-expression of clones encoding Kir6.2, a K+ inward rectifier, and SUR1, a sulfonylurea receptor, reconstitutes elementary features of ATP-sensitive K+ (KATP) channels. However, the precise kinetic properties of Kir6.2/SUR1 clones remain unknown. Herein, intraburst kinetics of Kir6.2/SUR1 channel activity, heterologously co-expressed in COS cells, displayed mean closed times from 0.7 +/- 0.1 to 0.4 +/- 0.03 msec, and from 0.4 +/- 0.1 to 2.0 +/- 0.2 msec, and mean open times from 1.9 +/- 0.4 to 4.5 +/- 0.8 msec, and from 12.1 +/- 2.4 to 5.0 +/- 0.2 msec between -100 and -20 mV, and +20 to +80 mV, respectively. Burst duration for Kir6.2/SUR1 activity was 17. 9 +/- 1.8 msec with 5.6 +/- 1.5 closings per burst. Burst kinetics of the Kir6.2/SUR1 activity could be fitted by a four-state kinetic model defining transitions between one open and three closed states with forward and backward rate constants of 1905 +/- 77 and 322 +/- 27 sec-1 for intraburst, 61.8 +/- 6.6 and 23.9 +/- 5.8 sec-1 for interburst, 12.4 +/- 6.0 and 13.6 +/- 2.9 sec-1 for intercluster events, respectively. Intraburst kinetic properties of Kir6.2/SUR1 clones were essentially indistinguishable from pancreatic or cardiac KATP channel phenotypes, indicating that intraburst kinetics per se were insufficient to classify recombinant Kir6.2/SUR1 amongst native KATP channels. Yet, burst kinetic behavior of Kir6.2/SUR1 although similar to pancreatic, was different from that of cardiac KATP channels. Thus, expression of Kir6.2/SUR1 proteins away from the pancreatic micro-environment, confers the burst kinetic identity of pancreatic, but not cardiac KATP channels. This study reports the kinetic properties of Kir6.2/SUR1 clones which could serve in the further characterization of novel KATP channel clones.
编码内向整流钾通道蛋白Kir6.2和磺脲类受体SUR1的克隆共表达，可重建ATP敏感性钾通道（KATP通道）的基本特征。然而，Kir6.2/SUR1克隆的确切动力学特性仍不清楚。在此，在COS细胞中异源共表达的Kir6.2/SUR1通道活性的爆发内动力学显示，在-100至-20 mV以及+20至+80 mV之间，平均关闭时间分别为0.7±0.1至0.4±0.03毫秒，以及0.4±0.1至2.0±0.2毫秒，平均开放时间分别为1.9±0.4至4.5±0.8毫秒，以及12.1±2.4至5.0±0.2毫秒。Kir6.2/SUR1活性的爆发持续时间为17.9±1.8毫秒，每次爆发有5.6±1.5次关闭。Kir6.2/SUR1活性的爆发动力学可用一个四态动力学模型拟合，该模型定义了一个开放状态和三个关闭状态之间的转换，爆发内的正向和反向速率常数分别为1905±77和322±27秒-1，爆发间为61.8±6.6和23.9±5.8秒-1，簇间事件为12.4±6.0和13.6±2.9秒-1。Kir6.2/SUR1克隆的爆发内动力学特性与胰腺或心脏KATP通道表型基本无法区分，这表明爆发内动力学本身不足以将重组Kir6.2/SUR1归类于天然KATP通道。然而，Kir6.2/SUR1的爆发动力学行为虽然与胰腺的相似，但与心脏KATP通道不同。因此，在远离胰腺微环境的情况下表达Kir6.2/SUR1蛋白，赋予了其胰腺KATP通道而非心脏KATP通道的爆发动力学特征。本研究报告了Kir6.2/SUR1克隆的动力学特性，这可用于进一步表征新型KATP通道克隆。
