Résumé:
Bacteria have evolved numerous specialized multiprotein membrane nanomachines to interact with their environment. Among them, Type IV Filaments (TFF) superfamily has emerged as the "Swiss Army knife" of surface molecular machines, capable of mediating an array of cellular functions, including protein secretion, DNA uptake, host-cell adhesion, biofilm formation, prey killing, sensing and various forms of motility.
TFF are ubiquitous nanomachines essential for bacterial survival, however the mechanism triggering active pili synthesis remains unknown. Using a combination of in vivo single-cell analyses and high-resolution NMR spectroscopy, we showed that PilM (a cytoplasmic component of the machinery) consists of a molecular gate requiring a lock and key mechanism to insert the PilB extension motor and activate TFF machineries.
Using two evolutionary distant model systems, Myxococcus xanthus and Vibrio cholerae, we demonstrated that distinct activators, respectively the SgmX protein and the secondary messenger c-di-GMP, both act on the same binding interface situated in the N1D subdomain of PilB to facilitate its interaction with PilM.
Our findings reveal a conserved regulatory hub for TFF machineries, explaining how these nanomachines were co-opted into diverse cellular processes across evolution.