Reconstitution of the ATP-sensitive potassium channel of skeletal muscle. Activation by a G protein-dependent process.
Reconstitution of the ATP-sensitive potassium channel of skeletal muscle. Activation by a G protein-dependent process.
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DOI：
10.1085/jgp.94.3.445
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发表时间：
1989-09
期刊：
影响因子：
--
通讯作者：
Coronado R
中科院分区：
文献类型：
--
作者：
Parent L;Coronado R
用平面双层膜记录技术研究了三磷酸腺苷（ATP）对家兔骨骼肌横小管膜钾通道的抑制作用。除了K（ATP）的单通道特性外，我们还报告了其对Mg 2+和鸟苷-5 '-三磷酸类似物GTP-γ（γ）-S的调节。K（ATP）通道（a）在250 mM内部KCl和50 mM外部KCl中的电导率为67 pS，并且在大于50 mV的保持电位下微弱整流，（B）不被内部Ca 2+或膜去极化激活，（c）具有大于50的渗透率比PK/PNa，以及（d）被毫摩尔内部ATP抑制。K（ATP）的活性，测量作为时间的函数的开放通道的概率，是不稳定的，在所有的保持电位，并在几分钟内持续下降后，记录开始。在活性降低后，将GTP-y-S（100 μ M）添加到内侧重新激活K（ATP）通道，但仅是短暂的。在存在的内部1 mM Mg 2+，GTP-y-S产生持续的再激活持续20-45分钟。孵育纯化的t-小管囊泡与AlF 4增加的K（ATP）通道的活性，模仿的效果GTP-y-S。AlF_4的作用和GTP-γ-S加Mg ~（2+）对持续通道激活的需要表明，一种核苷酸结合G蛋白调节兔骨骼肌t-小管膜ATP敏感性K通道。
Potassium channels inhibited by adenosine-5'-trisphosphate, K(ATP), found in the transverse tubular membrane of rabbit skeletal muscle were studied using the planar bilayer recording technique. In addition to the single-channel properties of K(ATP) we report its regulation of Mg2+ and by the guanosine-5'-trisphosphate analogue, GTP-y(gamma)-S. The K(ATP) channel (a) has a conductance of 67 pS in 250 mM internal, 50 mM external KCl, and rectifies weakly at holding potentials more positive than 50 mV, (b) is not activated by internal Ca2+ or membrane depolarization, (c) has a permeability ratio PK/PNa greater than 50, and (d) is inhibited by millimolar internal ATP. Activity of K(ATP), measured as open channel probability as a function of time, was unstable at all holding potentials and decreases continuously within a few minutes after a recording is initiated. After a decrease in activity, GTP-y-S (100 microM) added to the internal side reactivated K(ATP) channels but only transiently. In the presence of internal 1 mM Mg2+, GTP-y-S produced a sustained reactivation lasting 20-45 min. Incubation of purified t-tubule vesicles with AlF4 increased the activity of K(ATP) channels, mimicking the effect of GTP-y-S. The effect of AlF4 and the requirement of GTP-y-S plus Mg2+ for sustained channel activation suggests that a nucleotide-binding G protein regulates ATP-sensitive K channels in the t-tuble membrane of rabbit skeletal muscle.