Rate-limiting transport of positively charged arginine residues through the Sec-machinery is integral to the mechanism of protein secretion
- University of Bristol, United Kingdom
- University of Oxford, United Kingdom
- University of Otago, New Zealand
Abstract
Transport of proteins across and into membranes is a fundamental biological process with the vast majority being conducted by the ubiquitous Sec machinery. In bacteria, this is usually achieved when the SecY-complex engages the cytosolic ATPase SecA (secretion) or translating ribosomes (insertion). Great strides have been made towards understanding the mechanism of protein translocation. Yet, important questions remain - notably, the nature of the individual steps that constitute transport, and how the proton-motive force (PMF) across the plasma membrane contributes. Here, we apply a recently developed high-resolution protein transport assay to explore these questions. We find that pre-protein transport is limited primarily by the diffusion of arginine residues across the membrane, particularly in the context of bulky hydrophobic sequences. This specific effect of arginine, caused by its positive charge, is mitigated for lysine which can be deprotonated and transported across the membrane in its neutral form. These observations have interesting implications for the mechanism of protein secretion, suggesting a simple mechanism through which the PMF can aid transport by enabling a 'proton ratchet', wherein re-protonation of exiting lysine residues prevents channel re-entry, biasing transport in the outward direction.
Data availability
All raw data generated during this study are included as supplementary files, and annotated with the figure they were used in.
Article and author information
Author details
A Sofia F Oliveira
Funding
Wellcome Trust (104632)
- William J Allen
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/S008349/1)
- Daniel W Watkins
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/N015126/1)
- Daniel W Watkins
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/M003604/1)
- Robin A Corey
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/I008675/1)
- William J Allen
- Ian Collinson
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2022, Allen 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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Rate-limiting transport of positively charged arginine residues through the Sec-machinery is integral to the mechanism of protein secretion
eLife 11:e77586.
https://doi.org/10.7554/eLife.77586
