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Structure of a bacterial quorum-sensing transcription factor complexed with pheromone and DNA

  • A Corrigendum to this article was published on 20 July 2011


Many proteobacteria are able to monitor their population densities through the release of pheromones known as N-acylhomoserine lactones. At high population densities, these pheromones elicit diverse responses that include bioluminescence, biofilm formation, production of antimicrobials, DNA exchange, pathogenesis and symbiosis1. Many of these regulatory systems require a pheromone-dependent transcription factor similar to the LuxR protein of Vibrio fischeri. Here we present the structure of a LuxR-type protein. TraR of Agrobacterium tumefaciens was solved at 1.66 Å as a complex with the pheromone N-3-oxooctanoyl-l-homoserine lactone (OOHL) and its TraR DNA-binding site. The amino-terminal domain of TraR is an α/β/α sandwich that binds OOHL, whereas the carboxy-terminal domain contains a helix–turn–helix DNA-binding motif. The TraR dimer displays a two-fold symmetry axis in each domain; however, these two axes of symmetry are at an approximately 90° angle, resulting in a pronounced overall asymmetry of the complex. The pheromone lies fully embedded within the protein with virtually no solvent contact, and makes numerous hydrophobic contacts with the protein as well as four hydrogen bonds: three direct and one water-mediated.

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Change history

  • 20 July 2011

    The name of author Katherine M. Pappas has been corrected in the HTML as described in the accompanying Corrigendum.


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This work was supported by Monsanto Company, the US Department of Energy, Office of Biological and Environmental Research, and a National Research Service Award to S.C.W.

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The authors declare that they have no competing financial interests.

Correspondence to Andrzej Joachimiak.

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Further reading

Figure 1: Functional and structural roles of amino acid residues in TraR.
Figure 2: Stereo view of the structure of the TraR–OOHL–DNA complex.
Figure 3: The pheromone-binding site.
Figure 4: Specific protein–nucleic acid contacts between the recognition helix and tra box DNA.


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