6SGY

Structure of EccB3 dimer from the ESX-3 core complex

Summary for 6SGY

• Entry DOI: 10.2210/pdb6sgy/pdb
• EMDB information: 10188
• Descriptor: ESX-3 secretion system protein EccB3 (1 entity in total)
• Functional Keywords: type vii secretion system esx-3 secretion system t7ss esx-3 mycobacterium smegmatis, membrane protein
• Biological source: Mycobacterium smegmatis (strain ATCC 700084 / mc(2)155)
• Total number of polymer chains: 2
• Total formula weight: 85493.51

Authors

Famelis, N.,Rivera-Calzada, A.,Llorca, O.,Geibel, S. (deposition date: 2019-08-05, release date: 2019-10-09, Last modification date: 2024-10-16)

Primary citation

Famelis, N.,Rivera-Calzada, A.,Degliesposti, G.,Wingender, M.,Mietrach, N.,Skehel, J.M.,Fernandez-Leiro, R.,Bottcher, B.,Schlosser, A.,Llorca, O.,Geibel, S.
Architecture of the mycobacterial type VII secretion system.
Nature, 576:321-325, 2019

PubMed Abstract: Host infection by pathogenic mycobacteria, such as Mycobacterium tuberculosis, is facilitated by virulence factors that are secreted by type VII secretion systems. A molecular understanding of the type VII secretion mechanism has been hampered owing to a lack of three-dimensional structures of the fully assembled secretion apparatus. Here we report the cryo-electron microscopy structure of a membrane-embedded core complex of the ESX-3/type VII secretion system from Mycobacterium smegmatis. The core of the ESX-3 secretion machine consists of four protein components-EccB3, EccC3, EccD3 and EccE3, in a 1:1:2:1 stoichiometry-which form two identical protomers. The EccC3 coupling protein comprises a flexible array of four ATPase domains, which are linked to the membrane through a stalk domain. The domain of unknown function (DUF) adjacent to the stalk is identified as an ATPase domain that is essential for secretion. EccB3 is predominantly periplasmatic, but a small segment crosses the membrane and contacts the stalk domain. This suggests that conformational changes in the stalk domain-triggered by substrate binding at the distal end of EccC3 and subsequent ATP hydrolysis in the DUF-could be coupled to substrate secretion to the periplasm. Our results reveal that the architecture of type VII secretion systems differs markedly from that of other known secretion machines, and provide a structural understanding of these systems that will be useful for the design of antimicrobial strategies that target bacterial virulence.

PubMed: 31597161
DOI: 10.1038/s41586-019-1633-1

Experimental method

ELECTRON MICROSCOPY (4.6 Å)