Dynamic coupling of fast channel gating with slow ATP-turnover underpins protein transport through the Sec translocon
Dynamic coupling of fast channel gating with slow ATP-turnover underpins protein transport through the Sec translocon
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DOI：
10.1038/s44318-023-00004-1
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发表时间：
2024-01-02
期刊：
影响因子：
11.4
通讯作者：
Fessl，Tomas
中科院分区：
文献类型：
--
作者：
Crossley，Joel A.;Allen，William J.;Fessl，Tomas
Sec易位子是用于多肽跨脂质双层运输或进入脂质双层的高度保守的膜组装体。在细菌中，通过核心通道复合物分泌-内膜中的SecYEG-由胞质ATP酶SecA提供动力。在这里，我们使用单分子荧光来询问SecYEG在SecA的整个ATP水解循环中的构象状态。我们发现SecYEG通道在开放和关闭状态之间的波动比ATP周转快得多（易位期间约20倍），SecA的核苷酸状态调节开放和关闭的速率。SecY变体PrlA 4表现出更快的转运但不受ATP酶速率影响，增加了开放状态下的停留时间，促进前蛋白扩散通过孔，从而提高易位效率。因此，快速SecYEG通道动力学通过能量景观的调节与SecA变构偶联，并在蛋白质转运中发挥不可或缺的作用。松耦合的ATP营业额SecA的SecYEG的动态特性是兼容的布朗-rachet易位机制，而不是严格的核苷酸依赖性的相互转换之间的不同静态的一个电源冲程。
The Sec translocon is a highly conserved membrane assembly for polypeptide transport across, or into, lipid bilayers. In bacteria, secretion through the core channel complex—SecYEG in the inner membrane—is powered by the cytosolic ATPase SecA. Here, we use single-molecule fluorescence to interrogate the conformational state of SecYEG throughout the ATP hydrolysis cycle of SecA. We show that the SecYEG channel fluctuations between open and closed states are much faster (~20-fold during translocation) than ATP turnover, and that the nucleotide status of SecA modulates the rates of opening and closure. The SecY variant PrlA4, which exhibits faster transport but unaffected ATPase rates, increases the dwell time in the open state, facilitating pre-protein diffusion through the pore and thereby enhancing translocation efficiency. Thus, rapid SecYEG channel dynamics are allosterically coupled to SecA via modulation of the energy landscape, and play an integral part in protein transport. Loose coupling of ATP-turnover by SecA to the dynamic properties of SecYEG is compatible with a Brownian-rachet mechanism of translocation, rather than strict nucleotide-dependent interconversion between different static states of a power stroke.