9ST8

Structure of IglFC:IglGN complex

Summary for 9ST8

• Entry DOI: 10.2210/pdb9st8/pdb
• Related: 9ST4
• Descriptor: IglF C-terminal domain, IglC N-terminal domain, MAGNESIUM ION, ... (7 entities in total)
• Functional Keywords: type vi secretion system spike contractile injection system francisella, toxin
• Biological source: Francisella tularensis subsp. novicida; More
• Total number of polymer chains: 8
• Total formula weight: 153929.82

Authors

Guiot, E.,Gueguen-Chaignon, V.,Bataille, L.,Fronzes, R.,Henry, T.,Terradot, T. (deposition date: 2025-09-26, release date: 2026-05-13, Last modification date: 2026-09-02)

Primary citation

Degabriel, M.,Guiot, E.,Marcotte, M.,Berthollier, C.,Soussan, D.,Bataille, L.,Journeau, C.,Ducret, A.,Dayet, S.,Mosnier, A.,Martin, A.,Gueguen-Chaignon, V.,Boisset, S.,Fronzes, R.,Terradot, L.,Henry, T.
IglF mediates type VI secretion system spike assembly and promotes Francisella virulence.
Proc.Natl.Acad.Sci.USA, 123:e2530804123-e2530804123, 2026

PubMed Abstract: Type VI secretion systems (T6SSs) are widely distributed among Gram-negative bacteria, where they mostly act to promote bacterial warfare. Bacteria from the genus possess T6SSs that phylogenetically diverge from all other T6SSs and constitute the T6SSii subtype. tularensis, the agent of tularemia, relies on its T6SS to secrete effectors into host cells. Despite the key role of this nanomachine in virulence, the structure of T6SSii and the mechanism underlying its assembly are still poorly understood. Here, using , we focused on understanding the structure and assembly of the spike, the most apical T6SS complex coupling effector delivery and membrane-puncturing activity. We solved the structure of the protein of unknown function, IglF, in complex with the N-terminal domain of IglG, the T6SSii PAAR protein. Interaction between IglF and IglG enabled the assembly of a mature T6SS spike complex both in and in a heterologous expression system. In contrast, disrupting IglF:IglG interactions prevented assembly of the PAAR protein with the central spike complex and invalidated T6SS assembly, as visualized by monitoring T6SS dynamics or secretion. Accordingly, IglF:IglG interactions were required for virulence in vitro and in a mouse model of tularemia. Altogether, our findings shed light on the assembly mechanism of the T6SSii spike complex and its importance in virulence.

PubMed: 42150076
DOI: 10.1073/pnas.2530804123

Experimental method

X-RAY DIFFRACTION (3.3 Å)