Mycobacterium tuberculosis secretes multiple virulence factors during infection via the general Sec and Tat pathways, and via specialized ESX secretion systems, also referred to as type VII secretion systems. The ESX-1 secretion system is an important virulence determinant because deletion of ESX-1 leads to attenuation of M. tuberculosis. ESX-1 secreted protein B (EspB) contains putative PE (Pro-Glu) and PPE (Pro-Pro-Glu) domains, and a C-terminal domain, which is processed by MycP1 protease during secretion. We determined the crystal structure of PE-PPE domains of EspB, which represents an all-helical, elongated molecule closely resembling the structure of the PE25-PPE41 heterodimer despite limited sequence similarity. Also, we determined the structure of full-length EspB, which does not have interpretable electron density for the C-terminal domain confirming that it is largely disordered. Comparative analysis of EspB in cell lysate and culture filtrates of M. tuberculosis revealed that mature secreted EspB forms oligomers. Electron microscopy analysis showed that the N-terminal fragment of EspB forms donut-shaped particles. These data provide a rationale for the future investigation of EspB's role in M. tuberculosis pathogenesis.
|Number of pages||9|
|Journal||Journal of Structural Biology|
|State||Published - Aug 1 2015|
Bibliographical noteFunding Information:
Authors thank staff members of Southeast Regional Collaborative Access Team (SER-CAT) at the Advanced Photon Source, Argonne National Laboratory, for assistance during data collection. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences , under Contract No. W-31-109-Eng-38 . We thank the EPFL Bioelectron Microscopy and Protein Crystallography Core Facilities, and the Swiss Light Source for beam time and excellent support. We acknowledge the University of Kentucky Protein Analytical Core that is supported by NIH/NIGMS grant P30GM110787 . This study was supported in part by NIH/NIGMS grant P20GM103486 to K.V.K. This study received funding from the Swiss National Science Foundation to S.T.C. ( 31003A-140778 ).
© 2015 Elsevier Inc.
- PE domain
- PPE domain
- Type VII secretion system
ASJC Scopus subject areas
- Structural Biology