Structure of the Helicobacter pylori Cag Type IV secretion system
- University of Michigan, United States
- Vanderbilt University School of Medicine, United States
Abstract
Bacterial type IV secretion systems (T4SSs) are molecular machines that can mediate interbacterial DNA transfer through conjugation and delivery of effector molecules into host cells. The Helicobacter pylori Cag T4SS translocates CagA, a bacterial oncoprotein, into gastric cells, contributing to gastric cancer pathogenesis. We report the structure of a membrane-spanning Cag T4SS complex, which contains three sub-complexes: a 14-fold symmetric outer membrane core complex (OMCC), 17-fold symmetric periplasmic ring complex (PRC), and stalk domain. Features that differ markedly from those of prototypical T4SSs include an expanded OMCC and unexpected symmetry mismatch between the OMCC and PRC. This structure is one of the largest bacterial secretion system complexes ever reported and illustrates the remarkable structural diversity that exists among bacterial T4SSs.
Data availability
The cryo-EM volumes have been deposited in the Electron Microscopy Data Bank under accession codes EMD-20023 (T4SS C1 reconstruction), EMD-20020 (Focused OMCC Reconstruction), EMD-20022 (OMCC Asymmetric Reconstruction), EMD-20021 (Focused PRC Reconstruction). Map coordinates have been deposited in the Protein Data Bank under accession numbers 6OEE (CagT), 6OEG (CagX), and 6ODI (CagY), 6OEF (O-layer), 6OEH (I-Layer), and 6ODJ (PRC).
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T4SS C1 reconstructionElectron Microscopy Data Bank, EMD-20023.
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Focused OMCC ReconstructionElectron Microscopy Data Bank, EMD-20020.
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OMCC Asymmetric ReconstructionElectron Microscopy Data Bank, EMD-20022.
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Focused PRC ReconstructionElectron Microscopy Data Bank, EMD-20021.
Article and author information
Author details
Funding
National Institute of Allergy and Infectious Diseases (AI118932)
- Timothy L Cover
- Melanie D Ohi
National Cancer Institute (CA116087)
- Timothy L Cover
Department of Veterans' Affairs (1I01BX004447)
- Timothy L Cover
National Institute of General Medical Sciences (GM103310)
- Melanie D Ohi
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Andrew P Carter, MRC Laboratory of Molecular Biology, United Kingdom
Publication history
- Received: April 11, 2019
- Accepted: June 17, 2019
- Accepted Manuscript published: June 18, 2019 (version 1)
- Version of Record published: July 10, 2019 (version 2)
Copyright
© 2019, Chung 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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Structure of the Helicobacter pylori Cag Type IV secretion system
eLife 8:e47644.
https://doi.org/10.7554/eLife.47644
Further reading
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- Cell Biology
- Microbiology and Infectious Disease
African trypanosomes proliferate as bloodstream forms (BSFs) and procyclic forms in the mammal and tsetse fly midgut, respectively. This allows them to colonise the host environment upon infection and ensure life cycle progression. Yet, understanding of the mechanisms that regulate and drive the cell replication cycle of these forms is limited. Using single-cell transcriptomics on unsynchronised cell populations, we have obtained high resolution cell cycle regulated (CCR) transcriptomes of both procyclic and slender BSF Trypanosoma brucei without prior cell sorting or synchronisation. Additionally, we describe an efficient freeze–thawing protocol that allows single-cell transcriptomic analysis of cryopreserved T. brucei. Computational reconstruction of the cell cycle using periodic pseudotime inference allowed the dynamic expression patterns of cycling genes to be profiled for both life cycle forms. Comparative analyses identify a core cycling transcriptome highly conserved between forms, as well as several genes where transcript levels dynamics are form specific. Comparing transcript expression patterns with protein abundance revealed that the majority of genes with periodic cycling transcript and protein levels exhibit a relative delay between peak transcript and protein expression. This work reveals novel detail of the CCR transcriptomes of both forms, which are available for further interrogation via an interactive webtool.
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- Epidemiology and Global Health
- Microbiology and Infectious Disease
Background:
Dog-mediated rabies is endemic across Africa causing thousands of human deaths annually. A One Health approach to rabies is advocated, comprising emergency post-exposure vaccination of bite victims and mass dog vaccination to break the transmission cycle. However, the impacts and cost-effectiveness of these components are difficult to disentangle.
Methods:
We combined contact tracing with whole-genome sequencing to track rabies transmission in the animal reservoir and spillover risk to humans from 2010-2020, investigating how the components of a One Health approach reduced the disease burden and eliminated rabies from Pemba Island, Tanzania. With the resulting high-resolution spatiotemporal and genomic data we inferred transmission chains and estimated case detection. Using a decision tree model we quantified the public health burden and evaluated the impact and cost-effectiveness of interventions over a ten-year time horizon.
Results:
We resolved five transmission chains co-circulating on Pemba from 2010 that were all eliminated by May 2014. During this period, rabid dogs, human rabies exposures and deaths all progressively declined following initiation and improved implementation of annual islandwide dog vaccination. We identified two introductions to Pemba in late 2016 that seeded re-emergence after dog vaccination had lapsed. The ensuing outbreak was eliminated in October 2018 through reinstated islandwide dog vaccination. While post-exposure vaccines were projected to be highly cost-effective ($256 per death averted), only dog vaccination interrupts transmission. A combined One Health approach of routine annual dog vaccination together with free post-exposure vaccines for bite victims, rapidly eliminates rabies, is highly cost-effective ($1657 per death averted) and by maintaining rabies freedom prevents over 30 families from suffering traumatic rabid dog bites annually on Pemba island.
Conclusions:
A One Health approach underpinned by dog vaccination is an efficient, cost-effective, equitable and feasible approach to rabies elimination, but needs scaling up across connected populations to sustain the benefits of elimination, as seen on Pemba, and for similar progress to be achieved elsewhere.
Funding:
Wellcome [207569/Z/17/Z, 095787/Z/11/Z, 103270/Z/13/Z], the UBS Optimus Foundation, the Department of Health and Human Services of the National Institutes of Health [R01AI141712] and the DELTAS Africa Initiative [Afrique One-ASPIRE/DEL-15-008] comprising a donor consortium of the African Academy of Sciences (AAS), Alliance for Accelerating Excellence in Science in Africa (AESA), the New Partnership for Africa's Development Planning and Coordinating (NEPAD) Agency, Wellcome [107753/A/15/Z], Royal Society of Tropical Medicine and Hygiene Small Grant 2017 [GR000892] and the UK government. The rabies elimination demonstration project from 2010-2015 was supported by the Bill & Melinda Gates Foundation [OPP49679]. Whole-genome sequencing was partially supported from APHA by funding from the UK Department for Environment, Food and Rural Affairs (Defra), Scottish government and Welsh government under projects SEV3500 & SE0421.
