cb500744m_si_001.pdf (6.2 MB)
Structural Details of Light Activation of the LOV2-based Photoswitch PA-Rac1
journal contribution
posted on 2015-02-20, 00:00 authored by Andreas Winkler, Thomas
R. M. Barends, Anikó Udvarhelyi, Daniel Lenherr-Frey, Lukas Lomb, Andreas Menzel, Ilme SchlichtingOptical 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.