The bacterial translocon SecYEG opens upon ribosome binding.
The bacterial translocon SecYEG opens upon ribosome binding.
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DOI：
10.1074/jbc.m113.477893
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发表时间：
2013-06-21
期刊：
影响因子：
--
通讯作者：
Pohl P
中科院分区：
文献类型：
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作者：
Knyazev DG;Lents A;Krause E;Ollinger N;Siligan C;Papinski D;Winter L;Horner A;Pohl P
背景：SecYEG如何开启共翻译易位尚不清楚。结果：核糖体结合SecY复合体诱导离子通道活性。结论：SecYEG通过构象转变响应配体结合。意义：塞的错位为新生链的进入做了准备。在共翻译易位中，核糖体漏斗和蛋白质易位复合体SecYEG通道是对齐的。为了使新生链在合成后立即进入通道，一个尚未识别的信号触发SecYEG密封塞从孔中位移。在这里，我们发现核糖体结合到静止的SecYEG通道触发了这种构象转变。纯化和重组的SecYEG通道打开形成一个大的离子导电通道，其具有插头缺失突变体的导电性。每次融合事件插入平面双层的离子传导通道的数量大致等于单个蛋白脂质体中荧光相关光谱计算的SecYEG通道的数量。因此，通道的打开概率必须接近于1。为了防止致命的质子泄漏，必须存在与核糖体结合的SecYEG复合体的封闭翻译后构象。
Background: How SecYEG opens for co-translational translocation is unknown. Results: Ribosome binding to the SecY complex induces ion channel activity. Conclusion: SecYEG responds to ligand binding by a conformational transition. Significance: Dislocation of the plug prepares entry of the nascent chain. In co-translational translocation, the ribosome funnel and the channel of the protein translocation complex SecYEG are aligned. For the nascent chain to enter the channel immediately after synthesis, a yet unidentified signal triggers displacement of the SecYEG sealing plug from the pore. Here, we show that ribosome binding to the resting SecYEG channel triggers this conformational transition. The purified and reconstituted SecYEG channel opens to form a large ion-conducting channel, which has the conductivity of the plug deletion mutant. The number of ion-conducting channels inserted into the planar bilayer per fusion event roughly equals the number of SecYEG channels counted by fluorescence correlation spectroscopy in a single proteoliposome. Thus, the open probability of the channel must be close to unity. To prevent the otherwise lethal proton leak, a closed post-translational conformation of the SecYEG complex bound to a ribosome must exist.