This family consists of several Bacteriophage lambda Kil protein like sequences from both phages and bacteria. Induction of a lambda prophage causes the death of the host cell even in the absence of phage replication and lytic functions due to expression of the lambda kil gene [1].

1: Cell toxicity caused by products of the p(L) operon of bacteriophage lambda. Sergueev K, Yu D, Austin S, Court D; Gene 2001;272:227-235. PMID:11470529

2: Cold-sensitive phenotype of Escherichia coli cells harboring a plasmid carrying the kil gene of phage lambda brought under control of cI857 gene promoters. Sugino Y, Morita M; Gene 1994;141:25-30. PMID:8163171