RnlA_toxin is an RNase LS and a putative toxin of a bacterial toxin-antitoxin pair. Toxin-antitoxin systems consist of a stable toxin and an unstable antitoxin. In this case, a novel type II system, RnlA is the stable toxin that causes inhibition of cell growth and rapidly degrades T4 late mRNAs to prevent their expression, and this is neutralised by the activity of the unstable antitoxin RnlB [1, 2].

1: Regulation of growth and death in Escherichia coli by toxin-antitoxin systems. Yamaguchi Y, Inouye M; Nat Rev Microbiol. 2011;9:779-790. PMID:21927020

2: Escherichia coli rnlA and rnlB compose a novel toxin-antitoxin system. Koga M, Otsuka Y, Lemire S, Yonesaki T; Genetics. 2011;187:123-130. PMID:20980243