HDX-MS reveals nucleotide-based, anti-correlated opening and closure of SecA/ SecY channels of the bacterial translocon
- King's College London, United Kingdom
- University of Bristol, United Kingdom
- University of Oxford, United Kingdom
Abstract
The bacterial Sec translocon is a multi-protein complex responsible for translocating diverse proteins across the plasma membrane. For post-translational protein translocation, the Sec-channel - SecYEG - associates with the motor protein SecA to mediate the ATP-dependent transport of pre-proteins across the membrane. Previously, a diffusional based Brownian ratchet mechanism for protein secretion has been proposed [Allen et al. eLife 2016;5:e15598]; the structural dynamics required to facilitate this mechanism remain unknown. We employ hydrogen-deuterium exchange mass spectrometry (HDX-MS) to reveal striking nucleotide-dependent conformational changes in the Sec protein-channel from Escherichia coli. In addition to the ATP-dependent opening of SecY, reported previously, we observe a counteracting, and ATP-dependent, constriction of SecA around the pre-protein. ATP binding causes SecY to open and SecA to close; while, ADP produced by hydrolysis, has the opposite effect. This alternating behaviour could help impose the directionality of the Brownian ratchet for protein transport through the Sec machinery.
Data availability
All data generated or analysed during this study are included in the manuscript and as supplementary figures and tables. Raw HDX-MS proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE31 partner repository with the dataset identifier: PXD013594.
Article and author information
Author details
William John Allen
Funding
Wellcome (109854/Z/15/Z)
- Argyris Politis
Medical Research Council (MC_PC_15031)
- Argyris Politis
Biotechnology and Biological Sciences Research Council (BB/N015126/1)
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/M003604/1)
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/I008675/1)
- Ian Collinson
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Ahdash et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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HDX-MS reveals nucleotide-based, anti-correlated opening and closure of SecA/ SecY channels of the bacterial translocon
eLife 8:e47402.
https://doi.org/10.7554/eLife.47402
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