Biology subjects

Chabalier, M.

Publications and source records attributed to Chabalier, M..

3 recordsLinked to original sources

bioRxiv2021

Dynamic proton-dependent motors power Type IX secretion and gliding adhesin movement in Flavobacterium

Motile bacteria usually rely on external apparatus like flagella for swimming or pili for twitching. By contrast, gliding bacteria do not rely on obvious surface appendages to move on solid surfaces. Flavobacterium johnsoniae and other bacteria in the Bacteroidetes phylum use adhesins whose movement on the cell surface supports motility. In F. johnsoniae, secretion and helicoidal motion of the main adhesin SprB are intimately linked and depend on the type IX secretion system (T9SS). Both processes necessitate the proton motive force (PMF), which is thought to fuel a molecular motor that comprises the GldL and GldM cytoplasmic membrane proteins. Here we show that F. johnsoniae gliding motility is powered by the pH gradient component of the PMF. We further delineate the interaction network between the GldLM transmembrane helices (TMH) and show that conserved glutamate residues in GldL TMH are essential for gliding motility, although having distinct roles in SprB secretion and motion. We then demonstrate that the PMF and GldL trigger conformational changes in the GldM periplasmic domain. We finally show that multiple GldLM complexes are distributed in the membrane suggesting that a network of motors may be present to move SprB along a helical path on the cell surface. Altogether, our results provide evidence that GldL and GldM assemble dynamic membrane channels that use the proton gradient to power both T9SS-dependent secretion of SprB and its motion at the cell surface.

microbiology↗

bioRxiv2020

Central role and structure of the membrane pseudokinase YukC in the antibacterial Bacillus subtilis Type VIIb Secretion System.

Type VIIb Secretion System (T7SSb) has been recently identified in Firmicutes resembling the mycobacterial T7SSa. Despite limited sequence homology, T7SSa and T7SSb have substrates with striking structural similarities, the WXG100 proteins. Recent advances in Staphylococcus spp. proposed that T7SSb is involved in intra-species competition. However, the architecture and mechanism of action of this secretion complex remain largely obscure. Here, we investigate the T7SSb of Bacillus subtilis as a model system. We report the first evidence of B. subtilis ability to mediate intra- and inter-species antibacterial activity in a T7SSb-dependent manner. Then, we present the first systematic investigation of the T7SSb protein-protein network, revealing novel interactions and highlighting the central role of the pseudokinase subunit YukC in the assembly of the system. Its direct interaction with a T7SSb-secreted toxin supports its role in recruiting substrates to the secretion machinery. Finally, we solved the crystal structure of full-length transmembrane YukC defining novel structural motifs and suggesting that intrinsic flexibility modulates the orientation of the pseudokinase domains and YukC function. Overall, our results provide a better understanding on the role and molecular organisation of the T7SSb, opening new perspectives for the comprehension of this poorly characterized molecular machine.

microbiology↗

bioRxiv2018

A conserved motif of Porphyromonas Type IX secretion effectors C-terminal secretion signal specifies interactions with the PorKLMN core complex

The Type IX secretion system (T9SS) is a versatile protein transport apparatus restricted to the Bacteroidetes phylum. This multiprotein complex enables secretion of a wide range of effectors, such as protein toxins, filamentous adhesins, enzymes or S-layer subunits. Once translocated in the periplasm through the Sec pathway, recognition and secretion of these cargo proteins rely on a conserved C-terminal domain referred as CTD. However, the precise route followed by the CTD substrates from the periplasm to the cell exterior is yet to be determined. Here we define the interaction network of five different CTDs from the oral pathogen Porphyromonas gingivalis with the PorKLMN T9SS trans-envelope complex. We show that these five CTDs interact with the inner membrane-anchored PorM and the PorN periplasmic proteins. We further determine the contribution of the PorM IgG-like periplasmic domains and CTD conserved motifs for PorM-CTD complex formation. These results showed that all five CTDs interact with the core complex in a similar manner, suggesting a conserved mechanism of substrate selection in the periplasm. Our results thus establish a first model of the path followed by the CTD substrates through the T9SS.

microbiology↗