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]. This entry represents the C-terminal DBD domain, responsible for the RNA cleavage activity and toxicity. Through interaction between DBDs, RnlA dimerises in solution. T4 Dmd binds to DBD for inhibition of RnlA toxicity and RnlB also inhibits the toxicity of DBD [3].

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

3: RnlB Antitoxin of the Escherichia coli RnlA-RnlB Toxin-Antitoxin Module Requires RNase HI for Inhibition of RnlA Toxin Activity. Naka K, Qi D, Yonesaki T, Otsuka Y; Toxins (Basel). 2017; [Epub ahead of print] PMID:28085056