The Structure of YnaI Implies Structural and Mechanistic Conservation in the MscS Family of Mechanosensitive Channels.
The Structure of YnaI Implies Structural and Mechanistic Conservation in the MscS Family of Mechanosensitive Channels.
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DOI：
10.1016/j.str.2015.06.023
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发表时间：
2015-09-01
期刊：
影响因子：
--
通讯作者：
Rasmussen T
中科院分区：
文献类型：
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作者：
Böttcher B;Prazak V;Rasmussen A;Black SS;Rasmussen T
机械敏感性通道保护细菌免受周围环境中渗透压突然下降引起的裂解。除了大电导通道（MscL）和小电导通道（MscS）之外，大肠杆菌还有五个额外的MscS旁系同源物，它们在细菌界中具有功能并广泛存在。在这里，我们提出的结构YnaI的冷冻电子显微镜的分辨率为13 μ m。虽然胞质前庭在结构上与MscS相似，但在跨膜（TM）区域中观察到额外的密度，这与YnaI预测的两个额外TM螺旋的存在一致。这种密度的位置表明额外的TM螺旋是倾斜的，这可能会导致局部膜弯曲，延长在MscS中看到的张力感应桨。观察到偏离中心的脂质可触及腔，类似于MscS中传感器桨之间的间隙。YnaI中锥形形状和空腔的守恒表明了与MscS相似的机制。第一个结构的一个大成员的MscS家族的机械敏感通道密度图表明延伸传感器桨的倾斜跨膜螺旋脂质进入核心的Yna I和填充空腔，这是类似的差距在MscS这些空腔和倾斜的螺旋可以奠定基础的张力传感MscS家族的机械敏感通道被发现在所有王国的生活和保护细菌免受渗透压休克。Böttcher等人为更大的家族成员YnaI提供了第一个结构性的见解。尽管YnaI有额外的跨膜螺旋，重要的功能是保守的，这表明一个共同的机制。
Mechanosensitive channels protect bacteria against lysis caused by a sudden drop in osmolarity in their surroundings. Besides the channel of large conductance (MscL) and small conductance (MscS), Escherichia coli has five additional paralogs of MscS that are functional and widespread in the bacterial kingdom. Here, we present the structure of YnaI by cryo-electron microscopy to a resolution of 13 Å. While the cytosolic vestibule is structurally similar to that in MscS, additional density is seen in the transmembrane (TM) region consistent with the presence of two additional TM helices predicted for YnaI. The location of this density suggests that the extra TM helices are tilted, which could induce local membrane curvature extending the tension-sensing paddles seen in MscS. Off-center lipid-accessible cavities are seen that resemble gaps between the sensor paddles in MscS. The conservation of the tapered shape and the cavities in YnaI suggest a mechanism similar to that of MscS. First structure of a large member of the MscS family of mechanosensitive channels The density map indicates extended sensor paddles of tilted transmembrane helices Lipids access the core of YnaI and fill cavities which are similar to gaps in MscS These cavities and the tilted helices could lay the basis for tension sensing Mechanosensitive channels of the MscS family are found in all kingdoms of life and protect bacteria against osmotic shock. Böttcher et al. provide the first structural insights into a larger family member, YnaI. Despite YnaI having additional transmembrane helices, important features are conserved, suggesting a common mechanism.