This family consists of several bacterial zeta toxin proteins. Zeta toxin is thought to be part of a postregulational killing system in bacteria. It relies on antitoxin/toxin systems that secure stable inheritance of low and medium copy number plasmids during cell division and kill cells that have lost the plasmid [1].

1: Crystal structure of the plasmid maintenance system epsilon/zeta: functional mechanism of toxin zeta and inactivation by epsilon 2 zeta 2 complex formation. Meinhart A, Alonso JC, Strater N, Saenger W; Proc Natl Acad Sci U S A 2003;100:1661-1666. PMID:12571357