9MVG

Structure of SciW variant L66A bound to the Rhs1 transmembrane domain

Summary for 9MVG

• Entry DOI: 10.2210/pdb9mvg/pdb
• Descriptor: SciW protein, Rhs1 protein (3 entities in total)
• Functional Keywords: type vi secretion system, chaperone protein, chaperone-effector complex, secretion machinery, membrane protein, chaperone
• Biological source: Salmonella enterica subsp. enterica serovar Typhimurium; More
• Total number of polymer chains: 6
• Total formula weight: 80190.75

Authors

Van Schepdael, M.A.,Prehna, G. (deposition date: 2025-01-15, release date: 2026-01-28, Last modification date: 2026-02-18)

Primary citation

Van Schepdael, M.,Asakereh, I.,Colautti, J.,Gierys, A.J.,Sachar, K.,Ahmad, S.,Khajehpour, M.,Whitney, J.C.,Prehna, G.
Biophysical characterization of Eag chaperones suggests the mechanism of effector transmembrane domain release.
Nat Commun, 17:1401-1401, 2026

PubMed Abstract: The type VI secretion system (T6SS) is a dynamic protein nanomachine found in Gram-negative bacteria that secretes toxic effectors into prey-cells. For secretion, effectors require chaperones or adaptors for proper loading onto the T6SS. Effector associated genes (Eags) are a family of T6SS chaperones that stabilize N-terminal transmembrane domains (TMDs) found in thousands of effectors. Eags are essential for secretion and inhibit effector TMDs from prematurely adopting a membrane-penetrative conformation. However, the mechanism of TMD release from its cognate Eag chaperone is unknown. Here, we take a biochemical and biophysical approach to probe the mechanism of TMD binding and dissociation from Eag chaperones. Using steady-state fluorescence, stopped-flow measurements, and bacterial competition assays, we compare the thermodynamics, kinetics, and in vivo chaperone function of wild-type and point variant Eag-TMD complexes. Additionally, we solve an X-ray crystal structure of an Eag-TMD point variant complex that captures an intermediate state of TMD release. Our data reveals the molecular features and specific residue contacts necessary for TMD binding and demonstrates the Eag conformational change required to initiate rapid release of the TMD. Overall, our work details the stability of Eag-TMD complexes and the energetic pathway for the dissociation of effector TMDs from their Eag chaperones.

PubMed: 41571669
DOI: 10.1038/s41467-025-68138-w

Experimental method

X-RAY DIFFRACTION (3.05 Å)