Slow modal gating of single G protein-activated K+ channels expressed in Xenopus oocytes.
Slow modal gating of single G protein-activated K+ channels expressed in Xenopus oocytes.
复制标题
非洲爪蟾卵母细胞中表达的单 G 蛋白激活 K 通道的慢速模式门控。
DOI：
10.1111/j.1469-7793.2000.00737.x
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Dascal,N
中科院分区：
文献类型：
--
作者：
Yakubovich,D;Pastushenko,V;Bitler,A;Dessauer,CW;Dascal,N
1在单通道、由内而外的膜片中研究了爪蟾细胞中表达的 G 蛋白激活 K+ (GIRK) 通道的慢动力学。由 GIRK1 加 GIRK4 亚基形成的通道，已知可形成心脏乙酰胆碱 (ACh) 激活的 GIRK 通道 (KACh)，可被接近饱和剂量的 G 蛋白 βγ 亚基 (Gβγ；20 nM) 激活。2表达的 GIRK1/4 通道的动力学参数与心脏 KACh 的动力学参数相似。 GIRK1/4 通道与 GIRK1 与内源性卵母细胞亚基 GIRK5 (GIRK1/5) 形成的通道在某些动力学参数上存在显着差异，开放概率 Po 低 3 倍。 GIRK1/4 出人意料的低 Po（0.025）是由于存在数百毫秒的闭包；通道花费〜90％的时间处于长时间关闭状态。3GIRK1〜4通道显示出清晰的模态行为：在数十秒的时间尺度上，Gβγ激活通道在低Po模式（Poof约0.0034）和爆发模式之间循环，其特征是〜30倍高Po和一组不同的动力学常数（因此，一组不同的通道构象）。现有证据表明，缓慢的模态转换不是由 Gβγ 的结合和解离驱动的。4GTPγS 激活的 Gαi1 亚基先前被证明可以抑制 GIRK 通道，大大增加了关闭状态的时间，并且显然将通道转变为与低 Pomode 类似但不相同的模式。5这是 GIRK 通道中缓慢模态转换的首次证明。对 GIRK1∼4 慢门控动力学的详细描述可能有助于将来分析 GIRK 门控机制。
1The slow kinetics of G protein‐activated K+(GIRK) channels expressed inXenopusoocytes were studied in single‐channel, inside‐out membrane patches. Channels formed by GIRK1 plus GIRK4 subunits, which are known to form the cardiac acetylcholine (ACh)‐activated GIRK channel (KACh), were activated by a near‐saturating dose of G protein βγ subunits (Gβγ; 20 nM).2The kinetic parameters of the expressed GIRK1/4 channels were similar to those of cardiac KACh. GIRK1/4 channels differed significantly from channels formed by GIRK1 with the endogenous oocyte subunit GIRK5 (GIRK1/5) in some of their kinetic parameters and in a 3‐fold lower open probability,Po. The unexpectedly lowPo(0.025) of GIRK1/4 was due to the presence of closures of hundreds of milliseconds; the channel spent ∼90 % of the time in the long closed states.3GIRK1∼4 channels displayed a clear modal behaviour: on a time scale of tens of seconds, the Gβγ‐activated channels cycled between a low‐Pomode (Poof about 0.0034) and a bursting mode characterized by an ∼30‐fold higherPoand a different set of kinetic constants (and, therefore, a different set of channel conformations). The available evidence indicates that the slow modal transitions are not driven by binding and unbinding of Gβγ.4The GTPγS‐activated Gαi1subunit, previously shown to inhibit GIRK channels, substantially increased the time spent in closed states and apparently shifted the channel to a mode similar, but not identical, to the low‐Pomode.5This is the first demonstration of slow modal transitions in GIRK channels. The detailed description of the slow gating kinetics of GIRK1∼4 may help in future analysis of mechanisms of GIRK gating.