The structure of the endogenous ESX-3 secretion system.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31886769.
- Also identified by DOI 10.7554/eLife.52983 and PMC identifier 6986878.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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 <i>Mycobacterium smegmatis</i>. 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 EccB<sub>3</sub>, EccC<sub>3</sub>, and EccE<sub>3</sub> and two copies of the EccD<sub>3</sub> 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.
Medical subject headings
- Bacterial Proteins
- Mycobacterium smegmatis
- Protein Transport
- Type VII Secretion Systems