|Entry||Database: EMDB / ID: 3596|
|Title||The structure of the ESX-5 mycobacterial type VII secretion system membrane complex|
|Sample||ESX-5 T7SS membrane complex|
|Source||Mycobacterium xenopi rivm700367 / / bacteria|
|Method||single particle reconstruction / negative staining / 13.1 Å resolution|
|Authors||Ciccarelli L / Marlovits TC|
|Citation||Journal: Nat Microbiol / Year: 2017|
Title: Structure of the mycobacterial ESX-5 type VII secretion system membrane complex by single-particle analysis.
Authors: Katherine S H Beckham / Luciano Ciccarelli / Catalin M Bunduc / Haydyn D T Mertens / Roy Ummels / Wolfgang Lugmayr / Julia Mayr / Mandy Rettel / Mikhail M Savitski / Dmitri I Svergun / Wilbert Bitter / Matthias Wilmanns / Thomas C Marlovits / Annabel H A Parret / Edith N G Houben
Abstract: Mycobacteria are characterized by their impermeable outer membrane, which is rich in mycolic acids. To transport substrates across this complex cell envelope, mycobacteria rely on type VII (also ...Mycobacteria are characterized by their impermeable outer membrane, which is rich in mycolic acids. To transport substrates across this complex cell envelope, mycobacteria rely on type VII (also known as ESX) secretion systems. In Mycobacterium tuberculosis, these ESX systems are essential for growth and full virulence and therefore represent an attractive target for anti-tuberculosis drugs. However, the molecular details underlying type VII secretion are largely unknown, due to a lack of structural information. Here, we report the molecular architecture of the ESX-5 membrane complex from Mycobacterium xenopi determined at 13 Å resolution by electron microscopy. The four core proteins of the ESX-5 complex (EccB, EccC, EccD and EccE) assemble with equimolar stoichiometry into an oligomeric assembly that displays six-fold symmetry. This membrane-associated complex seems to be embedded exclusively in the inner membrane, which indicates that additional components are required to translocate substrates across the mycobacterial outer membrane. Furthermore, the extended cytosolic domains of the EccC ATPase, which interact with secretion effectors, are highly flexible, suggesting an as yet unseen mode of substrate interaction. Comparison of our results with known structures of other bacterial secretion systems demonstrates that the architecture of type VII secretion system is fundamentally different, suggesting an alternative secretion mechanism.
|Date||Deposition: Feb 17, 2017 / Header (metadata) release: Apr 5, 2017 / Map release: Apr 12, 2017 / Last update: Aug 2, 2017|
|Structure viewer||EM map: |
Downloads & links
|File||emd_3596.map.gz (map file in CCP4 format, 131073 KB)|
|Projections & slices|
Images are generated by Spider.
|Voxel size||X=Y=Z: 2.18 Å|
CCP4 map header:
-Entire ESX-5 T7SS membrane complex
|Entire||Name: ESX-5 T7SS membrane complex / Details: Solubilized in amphipol A8-35 / Number of components: 1|
|Mass||Theoretical: 1.8 MDa|
-Component #1: protein, ESX-5 T7SS membrane complex
|Protein||Name: ESX-5 T7SS membrane complex / Details: Solubilized in amphipol A8-35 / Recombinant expression: No|
|Mass||Theoretical: 1.8 MDa|
|Source||Species: Mycobacterium xenopi rivm700367 / / bacteria / Strain: RIVM700367|
|Source (engineered)||Expression System: Mycobacterium smegmatis str. mc2 155 / / bacteria|
|Specimen||Specimen state: particle / Method: negative staining|
|Sample solution||Specimen conc.: 0.1 mg/ml|
Buffer solution: 20 mM Tris pH 8, 100 mM NaCl, 5 % (v/v) glycerol
|Staining||A drop of 2% (w/v) uranyl acetate was added to a carbon-coated grid with absorbed protein and blotted after 30 s.|
|Vitrification||Cryogen name: NONE|
-Electron microscopy imaging
|Imaging||Microscope: FEI TECNAI 20|
|Electron gun||Electron source: LAB6 / Accelerating voltage: 200 kV / Electron dose: 20 e/Å2 / Illumination mode: FLOOD BEAM|
|Lens||Magnification: 50000 X (nominal), 44000 X (calibrated) / Cs: 1.2 mm / Imaging mode: BRIGHT FIELD / Defocus: 1400 - 5000 nm|
|Specimen Holder||Model: SIDE ENTRY, EUCENTRIC|
|Camera||Detector: FEI EAGLE (4k x 4k)|
|Image acquisition||Number of digital images: 65|
|Processing||Method: single particle reconstruction / Applied symmetry: C6 (6 fold cyclic) / Number of projections: 1418|
|3D reconstruction||Algorithm: BACK PROJECTION / Software: EMAN / Resolution: 13.1 Å / Resolution method: FSC 0.143 CUT-OFF|
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