Dynamic action of the Sec machinery during initiation, protein translocation and termination

Tomas Fessl, Dan W Watkins, Peter Oatley, William Allen, Robin Corey, Jim Horne, Steve A. Baldwin, Sheena E. Radford, Ian Collinson, Roman Tuma

Research output: Contribution to journalArticle (Academic Journal)peer-review

29 Citations (Scopus)
231 Downloads (Pure)


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.
Original languageEnglish
Article numbere35112
Number of pages68
Publication statusPublished - 7 Jun 2018


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