Mets, T.; Kurata, T.; Ernits, K.; Johansson, M. J. O.; Craig, S. Z.; Evora, G. M.; Buttress, J. A.; Odai, R.; Coppieters't Wallant, K.; Nakamoto, J. A.; Shyrokova, L.; Egorov, A. A.; Doering, C. R.; Brodiazhenko, T.; Laub, M. T.; Tenson, T.; Strahl, H.; Martens, C.; Harms, A.; Garcia-Pino, A.; Atkinson, G. C.; Hauryliuk, V.

Toxin-antitoxins (TAs) are prokaryotic two-gene systems comprised of a toxin neutralised by an antitoxin. Toxin-antitoxin-chaperone (TAC) systems additionally include a SecB-like chaperone that stabilises the antitoxin by recognising its chaperone addiction (ChAD) element. TACs have been shown to mediate antiphage defence, but the mechanisms of viral sensing and restriction are unexplored. We identify and characterise two Escherichia coli antiphage TAC systems containing HigBA and CmdTA TA units, HigBAC and CmdTAC. The HigBAC is triggered through recognition of the gpV major tail protein of phage lambda. Both the ChAD and gpV are recognised by the HigC chaperone through analogous aromatic molecular patterns, explaining the mechanism of activation. We show that the CmdT ADP-ribosyltransferase toxin modifies mRNA to shut down protein synthesis. We establish the modularity of TACs by creating a hybrid broad-spectrum antiphage system combining the CmdTA TA warhead with the HigC chaperone phage sensor.