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Publication Abstract from PubMed

Toxin YafQ functions as a ribonuclease in the dinJ-yafQ toxin-antitoxin system of Escherichia coli. Antitoxin DinJ neutralizes YafQ-mediated toxicity by forming a stable protein complex. Here, crystal structures of the (DinJ)2-(YafQ)2 complex and the isolated YafQ toxin have been determined. The structure of the heterotetrameric complex (DinJ)2-(YafQ)2 revealed that the N-terminal region of DinJ folds into a ribbon-helix-helix motif and dimerizes for DNA recognition, and the C-terminal portion of each DinJ exclusively wraps around a YafQ molecule. Upon incorporation into the heterotetrameric complex, a conformational change of YafQ in close proximity to the catalytic site of the typical microbial ribonuclease fold was observed and validated. Mutagenesis experiments revealed that a DinJ mutant restored YafQ RNase activity in a tetramer complex in vitro, but not in vivo. An electrophoretic mobility shift assay showed that one of the palindromic sequences present in the upstream intergenic region of DinJ served as a binding sequences for both the DinJ-YafQ complex and the antitoxin DinJ alone. Based on structure-guided and site-directed mutagenesis of DinJ-YafQ, we showed that two pairs of amino acids in DinJ were important for DNA binding: The R8A and K16A, and S31A and R35A substitutions in DinJ abolished the DNA binding ability of the DinJ-YafQ complex.

Structural and Functional Characterization of Escherichia coli Toxin-antitoxin Complex DinJ-YafQ.,Liang Y, Gao Z, Wang F, Zhang Y, Dong Y, Liu Q J Biol Chem. 2014 Jun 12. pii: jbc.M114.559773. PMID:24923448^[1]

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