Nature, Published online: 23 October 2024; doi:10.1038/s41586-024-08102-8

The bacterial anti-phage toxin–antitoxin–chaperone defence system CmdTAC senses capsid proteins via CmdC, enabling dissociation from the CmdTAC complex of the RNA ADP-ribosyltransferase CmdT, which targets single-stranded RNAs, inhibiting viral replication.