Dynamic action of the Sec machinery during initiation, protein translocation and termination.
Dynamic action of the Sec machinery during initiation, protein translocation and termination.
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作者：
Fessl T;Watkins D;Oatley P;Allen WJ;Corey RA;Horne J;Baldwin SA;Radford SE;Collinson I;Tuma R
蛋白质跨膜转运是蛋白质分泌和膜蛋白插入所需的普遍存在的过程。在细菌中，这主要是由保守的SecYEG复合物介导的，通过细胞质SecA和跨膜质子动力的ATP水解轮驱动。我们已经使用单分子技术来探索SecY孔动力学在多个时间尺度上，以解剖复杂的反应途径。结果表明，SecA，信号序列和前蛋白的成熟组分，以及ATP水解在通道解锁，开放和启动转运中均具有重要和特定的作用。通道开放后，易位过程分为两个阶段：一个缓慢的阶段，独立于基板长度，和长度依赖性运输阶段的固有易位率约为每秒40个氨基酸的proOmpA基板。广泛的易位率分布反映了多肽转运的随机性。
Protein translocation across cell membranes is a ubiquitous process required for protein secretion and membrane protein insertion. In bacteria, this is mostly mediated by the conserved SecYEG complex, driven through rounds of ATP hydrolysis by the cytoplasmic SecA, and the trans-membrane proton motive force. We have used single molecule techniques to explore SecY pore dynamics on multiple timescales in order to dissect the complex reaction pathway. The results show that SecA, both the signal sequence and mature components of the pre-protein, and ATP hydrolysis each have important and specific roles in channel unlocking, opening and priming for transport. After channel opening, translocation proceeds in two phases: a slow phase independent of substrate length, and a length-dependent transport phase with an intrinsic translocation rate of ~40 amino acids per second for the proOmpA substrate. Broad translocation rate distributions reflect the stochastic nature of polypeptide transport.