Article abstract
Nature Chemical Biology 4, 491 - 497 (2008)
Published online: 6 July 2008 | doi:10.1038/nchembio.99
Estimation of the available free energy in a LOV2-J
photoswitch
Xiaolan Yao1, Michael K Rosen1,2,3 & Kevin H Gardner1,3
Abstract
Protein photosensors are versatile tools for studying ligand-regulated allostery and signaling. Fundamental to these processes is the amount of energy that can be provided by a photosensor to control downstream signaling events. Such regulation is exemplified by the phototropins—plant serine/threonine kinases that are activated by blue light via conserved LOV (light, oxygen and voltage) domains. The core photosensor of oat phototropin 1 is a LOV domain that interacts in a light-dependent fashion with an adjacent 
-helix (J) to control kinase activity. We used solution NMR measurements to quantify the free energy of the LOV domain–J-helix binding equilibrium in the dark and lit states. These data indicate that light shifts this equilibrium by 
3.8 kcal mol-1, thus quantifying the energy available through LOV-J for light-driven allosteric regulation. This study provides insight into the energetics of light sensing by phototropins and benchmark values for engineering photoswitchable systems based on the LOV-J interaction.
- Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8816, USA.
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8816, USA.
- Department of Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8816, USA.
Correspondence to: Kevin H Gardner1,3 e-mail: kevin.gardner@utsouthwestern.edu
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