Inter-membrane association of the Sec and BAM translocons for bacterial outer-membrane biogenesis
- University of Bristol, United Kingdom
- Francis Crick Institute, United Kingdom
- Imperial College London, United Kingdom
- University of Exeter, United Kingdom
Abstract
The outer-membrane of Gram-negative bacteria is critical for surface adhesion, pathogenicity, antibiotic resistance and survival. The major constituent – hydrophobic b-barrel Outer-Membrane Proteins (OMPs) – are first secreted across the inner-membrane through the Sec-translocon for delivery to periplasmic chaperones e.g. SurA, which prevent aggregation. OMPs are then offloaded to the b-Barrel Assembly Machinery (BAM) in the outer-membrane for insertion and folding. We show the Holo-TransLocon (HTL) – an assembly of the protein-channel core-complex SecYEG, the ancillary sub-complex SecDF, and the membrane 'insertase' YidC – contacts BAM through periplasmic domains of SecDF and YidC, ensuring efficient OMP maturation. Furthermore, the proton-motive-force (PMF) across the inner-membrane acts at distinct stages of protein secretion: (1) SecA-driven translocation through SecYEG; and (2) communication of conformational changes via SecDF across the periplasm to BAM. The latter presumably drives efficient passage of OMPs. These interactions provide insights of inter-membrane organisation and communication, the importance of which is becoming increasingly apparent.
Data availability
All data generated or analysed during this study are included in the manuscript and supplementary information. Information regarding statistical testing is located in materials and methods and corresponding figure legends.
Article and author information
Author details
James Stuart Lorriman
Funding
Biotechnology and Biological Sciences Research Council (BB/S008349/1)
- Sara Alvira
EMBO (LTFCOFUND2013)
- Sara Alvira
EMBO (GA-2013-609409)
- Sara Alvira
Biotechnology and Biological Sciences Research Council (BB/S008349/1)
- Daniel W Watkins
Biotechnology and Biological Sciences Research Council (BB/S008349/1)
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/N015126/1)
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/N015126/1)
- Daniel W Watkins
Biotechnology and Biological Sciences Research Council (BB/M003604/1)
- Ian Collinson
Biotechnology and Biological Sciences Research Council (BB/M003604/1)
- Sara Alvira
Biotechnology and Biological Sciences Research Council (BB/J014400/1)
- Luca A Troman
EMBO (ALTF 710-2015)
- Sara Alvira
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Alvira 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.
Metrics
-
- 3,582
- views
-
- 591
- downloads
-
- 38
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Inter-membrane association of the Sec and BAM translocons for bacterial outer-membrane biogenesis
eLife 9:e60669.
https://doi.org/10.7554/eLife.60669
Further reading
-
- Biochemistry and Chemical Biology
Glycans play an important role in modulating the interactions between natural killer cells and antibodies to fight pathogens and harmful cells.
-
- Biochemistry and Chemical Biology
- Cell Biology
The Sonic hedgehog (Shh) signaling pathway controls embryonic development and tissue homeostasis after birth. This requires regulated solubilization of dual-lipidated, firmly plasma membrane-associated Shh precursors from producing cells. Although it is firmly established that the resistance-nodulation-division transporter Dispatched (Disp) drives this process, it is less clear how lipidated Shh solubilization from the plasma membrane is achieved. We have previously shown that Disp promotes proteolytic solubilization of Shh from its lipidated terminal peptide anchors. This process, termed shedding, converts tightly membrane-associated hydrophobic Shh precursors into delipidated soluble proteins. We show here that Disp-mediated Shh shedding is modulated by a serum factor that we identify as high-density lipoprotein (HDL). In addition to serving as a soluble sink for free membrane cholesterol, HDLs also accept the cholesterol-modified Shh peptide from Disp. The cholesteroylated Shh peptide is necessary and sufficient for Disp-mediated transfer because artificially cholesteroylated mCherry associates with HDL in a Disp-dependent manner, whereas an N-palmitoylated Shh variant lacking C-cholesterol does not. Disp-mediated Shh transfer to HDL is completed by proteolytic processing of the palmitoylated N-terminal membrane anchor. In contrast to dual-processed soluble Shh with moderate bioactivity, HDL-associated N-processed Shh is highly bioactive. We propose that the purpose of generating different soluble forms of Shh from the dual-lipidated precursor is to tune cellular responses in a tissue-type and time-specific manner.
