Phage single-stranded DNA-binding protein or host DNA damage triggers the activation of the AbpAB phage defense system.

Although numerous phage defense systems have recently been discovered in bacteria, how these systems defend against phage propagation or sense phage infections remains unclear. The AbpAB defense system targets several lytic and lysogenic phages harboring DNA genomes. A phage-encoded single-stranded DNA-binding protein, Gp32, activates this system similar to other phage defense systems such as Retron-Eco8, Hachiman, ShosTA, Nhi, and Hna.