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Mol Microbiol. 2011 Oct;82(1):251-64. doi: 10.1111/j.1365-2958.2011.07813.x. Epub 2011 Sep 12.

Atypical DNA recognition mechanism used by the EspR virulence regulator of Mycobacterium tuberculosis.

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Global Health Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.


The human pathogen Mycobacterium tuberculosis requires the ESX-1 secretion system for full virulence. EspR plays a key role in ESX-1 regulation via direct binding and transcriptional activation of the espACD operon. Here, we describe the crystal structures of EspR, a C-terminally truncated form, EspRΔ10, as well as an EspR-DNA complex. EspR forms a dimer with each monomer containing an N-terminal helix-turn-helix DNA binding motif and an atypical C-terminal dimerization domain. Structural studies combined with footprinting experiments, atomic force microscopy and molecular dynamic simulations allow us to propose a model in which a dimer of EspR dimers is the minimal functional unit with two subunits binding two consecutive major grooves. The other two DNA binding domains are thus free to form higher-order oligomers and to bridge distant DNA sites in a cooperative way. These features are reminiscent of nucleoid-associated proteins and suggest a more general regulatory role for EspR than was previously suspected.

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