This family represents a conserved region approximately 180 residues long within bacterial S-type pyocins. Pyocins are polypeptide toxins produced by, and active against, bacteria. S-type pyocins cause cell death by DNA breakdown due to endonuclease activity [1].

1: The pyocins of Pseudomonas aeruginosa. Michel-Briand Y, Baysse C; Biochimie 2002;84:499-510. PMID:12423794