Download MendeleyStructural mechanism of transcriptional autorepression of the Escherichia coli RelB/RelE antitoxin/toxin module.
Li, G.Y., Zhang, Y., Inouye, M., Ikura, M.(2008) J Mol Biol 380: 107-119
- PubMed: 18501926
- DOI: https://doi.org/10.1016/j.jmb.2008.04.039
- Primary Citation of Related Structures:
2K29 - PubMed Abstract:
The Escherichia coli chromosomal relBE operon encodes a toxin-antitoxin system, which is autoregulated by its protein products, RelB and RelE. RelB acts as a transcriptional repressor and RelE functions as a cofactor to enhance the repressor activity of RelB. Here, we present the NMR-derived structure of a RelB dimer and show that a RelB dimer recognizes a hexad repeat in the palindromic operator region through a ribbon-helix-helix motif. Our biochemical data show that two weakly associated RelB dimers bind to the adjacent repeats in the 3'-site of the operator (O(R)) at a moderate affinity (K(d), approximately 10(-5) M). However, in the presence of RelE, a RelB tetramer binds two distinct binding sites within the operator region, each with an enhanced affinity (K(d), approximately 10(-6) M for the low-affinity site, O(L), and 10(-8) M for the high-affinity site, O(R)). We propose that the enhanced affinity for the operator element is mediated by a cooperative DNA binding by a pair of RelB dimers and that the interaction between RelB dimers is strongly augmented by the presence of the cognate toxin RelE.
Organizational Affiliation:
Division of Signaling Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
