SspE-mediated immune defense: GTP hydrolysis as an allosteric switch coupling phosphorothioate recognition to DNA cleavage

3234/A. We elucidate its conserved "recognize-hydrolyze-activate" mechanism: the effector EcSspE integrates PT recognition, GTP hydrolysis, and allosteric signaling to license DNA cleavage. Beyond this paradigm, we reveal that subtle evolutionary refinements in its quaternary architecture-a streamlined, side-by-side assembly with a reduced interface-amplify defensive output by enhancing conformational dynamics. This insight bridges structural biophysics and immunity. The system's strict PT-dependence ensures biosafety, and its defined mechanistic logic and key molecular switches (Y63, R133, N724) establish a framework for engineering programmable phage resistance, advancing both our understanding of host-virus conflict and our ability to harness it.