title: Structural details of light activation of the LOV2-based photoswitch PA-Rac1.
abstract: Optical control of cellular processes is an emerging approach for studying biological systems, affording control with high spatial and temporal resolution. Specifically designed artificial photoswitches add an interesting extension to naturally occurring light-regulated functionalities. However, despite a great deal of structural information, the generation of new tools cannot be based fully on rational design yet; in many cases design is limited by our understanding of molecular details of light activation and signal transduction. Our biochemical and biophysical studies on the established optogenetic tool PA-Rac1, the photoactivatable small GTPase Rac1, reveal how unexpected details of the sensor-effector interface, such as metal coordination, significantly affect functionally important structural elements of this photoswitch. Together with solution scattering experiments, our results favor differences in the population of pre-existing conformations as the underlying allosteric activation mechanism of PA-Rac1, rather than the assumed release of the Rac1 domain from the caging photoreceptor domain. These results have implications for the design of new optogenetic tools and highlight the importance of including molecular details of the sensor-effector interface, which is however difficult to assess during the initial design of novel artificial photoswitches.
authors.affiliation: Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research , Jahnstrasse 29, 69120 Heidelberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Winkler
authors.forename: Thomas R M
authors.initials: TR
authors.lastname: Barends
authors.forename: Anikó
authors.initials: A
authors.lastname: Udvarhelyi
authors.forename: Daniel
authors.initials: D
authors.lastname: Lenherr-Frey
authors.forename: Lukas
authors.initials: L
authors.lastname: Lomb
authors.forename: Andreas
authors.initials: A
authors.lastname: Menzel
authors.forename: Ilme
authors.initials: I
authors.lastname: Schlichting
mesh_terms: D002118:Calcium / Q000737:chemistry; D008027:Light; D055537:Light Signal Transduction / Q000502:physiology*; D008670:Metals / Q000737:chemistry; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D020830:rac1 GTP-Binding Protein / Q000737:chemistry*
chemical_list: D008670:Metals; D020830:rac1 GTP-Binding Protein; D002118:Calcium