Straightening and sequential buckling of the pore-lining helices define the gating cycle of MscS
Straightening and sequential buckling of the pore-lining helices define the gating cycle of MscS
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DOI：
10.1038/nsmb1341
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发表时间：
2007-12-01
影响因子：
16.8
通讯作者：
Sukharev, Sergei
中科院分区：
文献类型：
--
作者：
Akitake, Bradley;Anishkin, Andriy;Sukharev, Sergei
我们描述了一种将细菌机械敏感通道MSCs的适应行为与毛孔衬里螺旋TM3的灵活性联系起来的机制。对通道结构的模拟膨胀揭示了在打开状态下Gly113附近的一个特征扭结变直；返回到关闭状态时在Gly121处产生了另一个扭结。膜片钳实验表明，G113A突变引入的更高的螺旋倾向防止了失活。一个类似的突变，G121A，在动力学上阻碍了关闭和失活。在这些部位复制甘氨酸以增加灵活性会产生直接相反的效果。剧毒的G113A G121A突变导致通道不能失活或随着紧张的释放而关闭。这些数据表明，开放的MSCs以TM3螺旋为特征，TM3螺旋起着可折叠的“支柱”的作用。闭合和脱敏依赖于Gly121处的屈曲，而Gly113处的晶状扭曲是失活状态的特征。
We describe a mechanism connecting the adaptive behavior of the bacterial mechanosensitive channel MscS to the flexibility of the pore-lining helix TM3. Simulated expansion of the channel structure revealed straightening of a characteristic kink near Gly113 in the open state; return to the closed state produced an alternative kink at Gly121. Patch-clamp experiments showed that higher helical propensity introduced by a G113A mutation prevented inactivation. A similar mutation, G121A, kinetically impeded both closure and inactivation. Duplicating the glycines at each of these sites to increase flexibility produced directly opposite effects. The severely toxic G113A G121A mutation resulted in channels that could not inactivate or close with the release of tension. These data suggest that the open MscS features straight TM3 helices, which act as collapsible 'struts'. Closure and desensitization rely on buckling at Gly121, whereas the crystal-like kink at Gly113 is a feature of the inactivated state.