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Updated: Jan 10, 2026

In-vitro Reconstitution of Bacterial Ubiquitination and VCP/p97-mediated Elimination
Published on: January 2, 2026
A ubiquitin-like protein controls assembly of a bacterial type VIIb secretion system
Gabriel U Oka1, Nathanaël Benoit1, Axel Siroy1,2
1CNRS UMR 5234 Microbiologie Fondamentale et Pathogénicité, Institut Européen de Chimie et Biologie, University of Bordeaux, 33600 Pessac, France.
Abstract:
Type VII secretion systems (T7SS) are protein translocation machines crucial for virulence and bacterial competition in Gram-positive bacteria. Despite their importance, the structural basis for assembly of type VIIb secretion systems (T7SSb), a widely distributed variant in Firmicutes, remains poorly understood. We present the cryo-electron microscopy structure of the T7SSb core complex from Bacillus subtilis, revealing how the ubiquitin-like protein YukD, coordinates assembly of the secretion machinery. YukD interacts extensively with the central channel component YukB and facilitates its association with the pseudokinase YukC, forming a stable building block for channel assembly. Time-lapse microscopy and competition assays demonstrate that YukD is essential for proper T7SSb complex formation and contact-dependent bacterial killing. Our findings reveal how bacteria have adapted a ubiquitin-like protein as a structural regulator for assembling a large secretion complex.
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