title: Estimation of the available free energy in a LOV2-J alpha photoswitch.
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 alpha-helix (J alpha) to control kinase activity. We used solution NMR measurements to quantify the free energy of the LOV domain-J alpha-helix binding equilibrium in the dark and lit states. These data indicate that light shifts this equilibrium by approximately 3.8 kcal mol(-1), thus quantifying the energy available through LOV-J alpha 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 alpha interaction.
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8816, USA.
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Yao
authors.forename: Michael K
authors.initials: MK
authors.lastname: Rosen
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Gardner
mesh_terms: D000494:Allosteric Regulation / Q000528:radiation effects*; D056931:Cryptochromes; D004789:Enzyme Activation / Q000528:radiation effects; D005420:Flavoproteins / Q000737:chemistry* / Q000528:radiation effects*; D008027:Light; D010100:Oxygen; D010940:Plant Proteins; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary / Q000528:radiation effects; D013816:Thermodynamics
chemical_list: D056931:Cryptochromes; D005420:Flavoproteins; D010940:Plant Proteins; D017346:Protein Serine-Threonine Kinases; D010100:Oxygen