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 N-terminal domain composed of four-stranded twisted antiparallel beta-sheet and two alpha-helices [3,4].

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

4: Structure-function studies of Escherichia coli RnlA reveal a novel toxin structure involved in bacteriophage resistance. Wei Y, Gao ZQ, Otsuka Y, Naka K, Yonesaki T, Zhang H, Dong YH; Mol Microbiol. 2013;90:956-965. PMID:24112600