期刊
STRUCTURE
卷 23, 期 3, 页码 571-583出版社
CELL PRESS
DOI: 10.1016/j.str.2015.01.002
关键词
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资金
- Canadian Foundation of Innovation
- British Columbia Knowledge Development Fund
- UBC Four-Year PhD Fellowship
- Canadian Institute of Health Research
- Howard Hughes Medical Institute International Scholar program
- Natural Sciences and Engineering Research Council of Canada
- Canadian Institutes for Health Research
- Michael Smith Foundation for Health Research
- Canadian Foundation for Innovation
- University of British Columbia
- Genome Canada/Genome British Columbia Technology Development Grant
Mycobacterium tuberculosis (Mtb) uses the ESX-1 type VII secretion system to export virulence proteins across its lipid-rich cell wall, which helps permeabilize the host's macrophage phagosomal membrane, facilitating the escape and cell-to-cell spread of Mtb. ESX-1 membranolytic activity depends on a set of specialized secreted Esp proteins, the structure and specific roles of which are not currently understood. Here, we report the X-ray and electron microscopic structures of the ESX-1-secreted EspB. We demonstrate that EspB adopts a PE/PPE-like fold that mediates oligomerization with apparent heptameric symmetry, generating a barrel-shaped structure with a central pore that we propose contributes to the macrophage killing functions of EspB. Our structural data also reveal unexpected direct interactions between the EspB bipartite secretion signal sequence elements that form a unified aromatic surface. These findings provide insight into how specialized proteins encoded within the ESX-1 locus are targeted for secretion, and for the first time indicate an oligomerization-dependent role for Esp virulence factors.
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