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Proc Natl Acad Sci U S A. 2011 Jun 7;108(23):9449-54. doi: 10.1073/pnas.1100262108. Epub 2011 May 23.

Structural basis of photosensitivity in a bacterial light-oxygen-voltage/helix-turn-helix (LOV-HTH) DNA-binding protein.

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  • 1Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-8816, USA.

Erratum in

  • Proc Natl Acad Sci U S A. 2012 Apr 10;109(15):5904.


Light-oxygen-voltage (LOV) domains are blue light-activated signaling modules integral to a wide range of photosensory proteins. Upon illumination, LOV domains form internal protein-flavin adducts that generate conformational changes which control effector function. Here we advance our understanding of LOV regulation with structural, biophysical, and biochemical studies of EL222, a light-regulated DNA-binding protein. The dark-state crystal structure reveals interactions between the EL222 LOV and helix-turn-helix domains that we show inhibit DNA binding. Solution biophysical data indicate that illumination breaks these interactions, freeing the LOV and helix-turn-helix domains of each other. This conformational change has a key functional effect, allowing EL222 to bind DNA in a light-dependent manner. Our data reveal a conserved signaling mechanism among diverse LOV-containing proteins, where light-induced conformational changes trigger activation via a conserved interaction surface.

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