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Publication Abstract from PubMed

Escherichia coli RnlA-RnlB is a newly identified toxin-antitoxin (TA) system that plays a role in bacteriophage resistance. RnlA functions as a toxin with mRNA endoribonuclease activity and the cognate antitoxin RnlB inhibits RnlA toxicity in E. coli cells. Interestingly, T4 phage encodes the antitoxin Dmd, which acts against RnlA to promote its own propagation, suggesting that RnlA-Dmd represents a novel TA system. Here, we have determined the crystal structure of RnlA refined to 2.10 A. RnlA is composed of three independent domains: NTD (N-terminal domain), NRD (N repeated domain) and DBD (Dmd binding domain), which is an organization not previously observed among known toxin structures. Small-angle X-ray scattering (SAXS) analysis revealed that RnlA forms a dimer in solution via interactions between the DBDs from both monomers. The in vitro and in vivo functional studies showed that among the three domains, only the DBD is responsible for recognition and inhibition by Dmd and subcellular location of RnlA. In particular, the helix located at the C-terminus of DBD plays a vital role in binding Dmd. Our comprehensive studies reveal the key region responsible for RnlA toxicity and provide novel insights into its structure-function relationship.

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 Sep 30. doi: 10.1111/mmi.12409. PMID:24112600^[5]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.