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J Biol Chem. 2014 Jul 25;289(30):20559-69. doi: 10.1074/jbc.M114.573006. Epub 2014 Jun 4.

Mechanisms of toxin inhibition and transcriptional repression by Escherichia coli DinJ-YafQ.

Author information

1
From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
2
From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322 christine.m.dunham@emory.edu.

Abstract

Bacteria encounter environmental stresses that regulate a gene expression program required for adaptation and survival. Here, we report the 1.8-Å crystal structure of the Escherichia coli toxin-antitoxin complex YafQ-(DinJ)2-YafQ, a key component of the stress response. The antitoxin DinJ dimer adopts a ribbon-helix-helix motif required for transcriptional autorepression, and toxin YafQ contains a microbial RNase fold whose proposed active site is concealed by DinJ binding. Contrary to previous reports, our studies indicate that equivalent levels of transcriptional repression occur by direct interaction of either YafQ-(DinJ)2-YafQ or a DinJ dimer at a single inverted repeat of its recognition sequence that overlaps with the -10 promoter region. Surprisingly, multiple YafQ-(DinJ)2-YafQ complexes binding to the operator region do not appear to amplify the extent of repression. Our results suggest an alternative model for transcriptional autorepression that may be novel to DinJ-YafQ.

KEYWORDS:

Bacterial Toxin; Energy Metabolism; Ribbon-Helix-Helix Factor; Stress Response; Toxin-Antitoxin Complexes; Transcription Repressor; X-ray Crystallography

PMID:
24898247
PMCID:
PMC4110269
DOI:
10.1074/jbc.M114.573006
[Indexed for MEDLINE]
Free PMC Article

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