Nucleotidyl transferase AbiEii toxin, Type IV TA system
This family was recently identified as belonging to the nucleotidyltransferase superfamily. AbiEii is the cognate toxin of the type IV toxin-antitoxin 'innate immunity' bacterial abortive infection (Abi) system that protects bacteria from the spread of a phage infection. The Abi system is activated upon infection with phage to abort the cell thus preventing the spread of phage through viral replication. There are some 20 or more Abis, and they are predominantly plasmid-encoded lactococcal systems. TA, toxin-antitoxin, systems on plasmids function by killing cells that lose the plasmid upon division. AbiE phage resistance systems function as novel Type IV TAs and are widespread in bacteria and archaea. The cognate antitoxin is pfam13338.
Jiyao W et al.(2023). "The conserved domain database in 2023.",