Abstract
Chitinases are important enzymes that contribute to the generation of carbon and nitrogen from chitin, a long chain polymer of N-acetylglucosamine that is abundant in insects, fungi, invertebrates and fish. Although mammals do not produce chitin, chitinases have been identified in bacteria that are key virulence factors in severe respiratory, gastrointestinal and urinary diseases. However, it is unclear how these enzymes are able to carry out this dual function. Legionella pneumophila is the causative agent of Legionnaires’ disease, an often-fatal pneumonia and its chitinase ChiA is essential for the survival of L. pneumophila in the lung. Here we report the first atomic resolution insight into the pathogenic mechanism of a bacterial chitinase. We derive an experimental model of intact ChiA and show how its N-terminal region targets ChiA to the bacterial surface after its secretion. We provide the first evidence that L. pneumophila can bind mucins on its surface, but this is not dependent on ChiA. This demonstrates that additional peripheral mucin binding proteins are also expressed in L. pneumophila. We also show that the ChiA C-terminal chitinase domain has novel Zn2+-dependent peptidase activity against mammalian mucin-like proteins, namely MUC5AC and the C1-esterase inhibitor, and that ChiA promotes bacterial penetration of mucin gels. Our findings suggest that ChiA can facilitate passage of L. pneumophila through the alveolar mucosa, can modulate the host complement system and that ChiA may be a promising target for vaccine development.
Original language | English (US) |
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Article number | e1008342 |
Journal | PLoS pathogens |
Volume | 16 |
Issue number | 5 |
DOIs | |
State | Published - May 2020 |
Funding
SR, KHR, RS and JAG were supported by the Medical Research Council (MR/M009920/1 and MR/R017662/1). PC was supported by the Academy of Medical Sciences/Wellcome Trust (SBF002/1150). TJP was supported by an Engineering and Physical Sciences Research Council studentship and BD was supported by a Biotechnology and Biological Sciences Research Council studentship. Work in the Cianciotto lab was supported by a National Institutes of Health grant R01AI 043987. LSG and RCW were also partly supported by National Institutes of Health training grants T32 GM08061 and T32 AI0007476, respectively. This work was supported by synchrotron access at the Diamond Light Source. The King’s College London Centre for Biomolecular Spectroscopy was funded by the Wellcome Trust. This work was also supported by the Francis Crick Institute through provision of access to the MRC Biomedical NMR Centre. The Francis Crick Institute receives its core funding from Cancer Research UK (FC001029), the UK Medical Research Council (FC001029), and the Wellcome Trust (FC001029). MD simulations were performed using time on ARCHER granted via High-End Computing Biomolecular Simulation Consortium, supported by Engineering and Physical Sciences Research Council (EP/R029407/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank the beamline scientists at I02, I04 and B21 of the Diamond Light Source for support during data acquisition and Dr Ben Stieglitz (Queen Mary University of London) for providing ITC support.
ASJC Scopus subject areas
- Parasitology
- Microbiology
- Immunology
- Molecular Biology
- Genetics
- Virology
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Crystal structure of the Legionella pneumophila ChiA C-terminal domain
Rehman, S. (Contributor), Grigoryeva, L. S. (Contributor), Richardson, K. H. (Contributor), Corsini, P. (Contributor), White, R. C. (Contributor), Shaw, R. (Contributor), Portlock, T. J. (Contributor), Dorgan, B. (Contributor), Zanjani, Z. S. (Contributor), Fornili, A. (Contributor), Cianciotto, N. P. (Contributor) & Garnett, J. A. (Contributor), Protein Data Bank (PDB), Apr 22 2020
DOI: 10.2210/pdb6S2X/pdb, https://www.wwpdb.org/pdb?id=pdb_00006s2x
Dataset