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Department of Microbiology and Physiological Systems

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Amino Acids, Peptides, and Proteins | Bacteria | Biophysics | Microbiology | Molecular Biology | Structural Biology


The ESX (or Type VII) secretion systems are protein export systems in mycobacteria and many Gram-positive bacteria that mediate a broad range of functions including virulence, conjugation, and metabolic regulation. These systems translocate folded dimers of WXG100-superfamily protein substrates across the cytoplasmic membrane. We report the cryo-electron microscopy structure of an ESX-3 system, purified using an epitope tag inserted with recombineering into the chromosome of the model organism Mycobacterium smegmatis. The structure reveals a stacked architecture that extends above and below the inner membrane of the bacterium. The ESX-3 protomer complex is assembled from a single copy of the EccB3, EccC3, and EccE3 and two copies of the EccD3 protein. In the structure, the protomers form a stable dimer that is consistent with assembly into a larger oligomer. The ESX-3 structure provides a framework for further study of these important bacterial transporters.


molecular biophysics, structural biology

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© 2019, Poweleit et al. Creative Commons Attribution 4.0 International (CC BY 4.0)

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Elife. 2019 Dec 30;8. pii: e52983. doi: 10.7554/eLife.52983. [Epub ahead of print] Link to article on publisher's site

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.