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Cryo-EM reveals the membrane-binding phenomenon of EspB, a virulence factor of the mycobacterial type VII secretion system

Sengupta, N and Padmanaban, S and Dutta, S (2023) Cryo-EM reveals the membrane-binding phenomenon of EspB, a virulence factor of the mycobacterial type VII secretion system. In: Journal of Biological Chemistry, 299 (4).

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Official URL: https://doi.org/10.1016/j.jbc.2023.104589


Mycobacterium tuberculosis (Mtb) utilizes sophisticated machinery called the type VII secretion system to translocate virulence factors across its complex lipid membrane. EspB, a ∼36 kDa secreted substrate of the ESX-1 apparatus, was shown to cause ESAT-6–independent host cell death. Despite the current wealth of high-resolution structural information of the ordered N-terminal domain, the mechanism of EspB-mediated virulence remains poorly characterized. Here, we document EspB interaction with phosphatidic acid (PA) and phosphatidylserine (PS) in the context of membranes, through a biophysical approach including transmission electron microscopy and cryo-EM. We were also able to show PA, PS-dependent conversion of monomers to oligomers at physiological pH. Our data suggest that EspB adheres to biological membranes with limited PA and PS. EM of yeast mitochondria with EspB indicates a mitochondrial membrane-binding property of this ESX-1 substrate. Further, we determined the 3D structures of EspB with and without PA and observed plausible stabilization of the low complexity C-terminal domain in the presence of PA. Collectively, our cryo-EM–based structural and functional studies of EspB provide further insight into the host–Mtb interaction.

Item Type: Journal Article
Publication: Journal of Biological Chemistry
Publisher: American Society for Biochemistry and Molecular Biology Inc.
Additional Information: The copyright for this article belongs to the Authors.
Keywords: Binding energy; Cell death; Cell membranes; High resolution transmission electron microscopy; Mitochondria; pH, Cryo-EM; Espb; ESX-1; Membrane binding; Mycobacteria; Phosphatidic acids; Phosphatidylserine; Secretion systems; T7SS; Virulence factors, Phospholipids
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 25 May 2023 07:39
Last Modified: 25 May 2023 07:39
URI: https://eprints.iisc.ac.in/id/eprint/81500

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