Molecular analysis of ATP-sensitive K channel gating and implications for channel inhibition by ATP.
Molecular analysis of ATP-sensitive K channel gating and implications for channel inhibition by ATP.
复制标题
DOI：
10.1085/jgp.112.3.333
复制
发表时间：
1998-09
期刊：
影响因子：
--
通讯作者：
Ashcroft FM
中科院分区：
文献类型：
--
作者：
Trapp S;Proks P;Tucker SJ;Ashcroft FM
β细胞KATP通道是由4个成孔亚基(Kir6.2)和4个调节亚基(SUR1)组成的八聚体复合体。Kir6.2(Kir6.2ΔC26)的截短亚型独立于SUR1表达，表现出内在的三磷酸腺苷敏感性，表明该亚基主要负责介导三磷酸腺苷的抑制。我们在这里表明，位于第二跨膜结构域的胞浆末端的C166突变为丝氨酸(C166S)，通过减少通道在长时间关闭状态的时间，使Kir6.2ΔC26的开放概率增加了近七倍。通道活跃度也降低了。含有C166S突变的Kir6.2ΔC26对三磷酸腺苷的敏感性显著降低：Ki由175mM降至2.8mM。C166位的苏氨酸、丙氨酸、蛋氨酸或苯丙氨酸的替代也降低了通道对ATP的敏感性，同时增加了通道的开放概率。因此，三磷酸腺苷不起开放通道阻滞剂的作用。在携带C166S突变的SUR1和Kir6.2组成的通道中，甲苯丁胺的抑制作用减弱。我们的结果与C166在通道的内在门控中发挥作用的想法是一致的，可能是通过影响位于毛孔内末端的门。动力学分析表明，当C166突变时，观察到的ATP敏感性的明显降低和其他性质的变化很大程度上是从开放状态到长时间关闭状态的受损转换的结果。
The β cell KATP channel is an octameric complex of four pore-forming subunits (Kir6.2) and four regulatory subunits (SUR1). A truncated isoform of Kir6.2 (Kir6.2ΔC26), which expresses independently of SUR1, shows intrinsic ATP sensitivity, suggesting that this subunit is primarily responsible for mediating ATP inhibition. We show here that mutation of C166, which lies at the cytosolic end of the second transmembrane domain, to serine (C166S) increases the open probability of Kir6.2ΔC26 approximately sevenfold by reducing the time the channel spends in a long closed state. Rundown of channel activity is also decreased. Kir6.2ΔC26 containing the C166S mutation shows a markedly reduced ATP sensitivity: the K i is reduced from 175 μM to 2.8 mM. Substitution of threonine, alanine, methionine, or phenylalanine at position C166 also reduced the channel sensitivity to ATP and simultaneously increased the open probability. Thus, ATP does not act as an open channel blocker. The inhibitory effects of tolbutamide are reduced in channels composed of SUR1 and Kir6.2 carrying the C166S mutation. Our results are consistent with the idea that C166 plays a role in the intrinsic gating of the channel, possibly by influencing a gate located at the intracellular end of the pore. Kinetic analysis suggests that the apparent decrease in ATP sensitivity, and the changes in other properties, observed when C166 is mutated is largely a consequence of the impaired transition from the open to the long closed state.
登录
查看更多内容
影响因子：
3.8
作者：
Holmgren, M;Smith, PL;Yellen, G
通讯作者：
Yellen, G
影响因子：
--
作者：
GILLIS, KD;GEE, WM;MISLER, S
通讯作者：
MISLER, S
影响因子：
3.8
作者：
Shyng, SL;Ferrigni, T;Nichols, CG
通讯作者：
Nichols, CG
影响因子：
3.8
作者：
Trapp, S;Tucker, SJ;Ashcroft, FM
通讯作者：
Ashcroft, FM
影响因子：
16.2
作者：
Liu, Y;Holmgren, M;Yellen, G
通讯作者：
Yellen, G