Mechanistic basis of the fast dark recovery of the short LOV protein DsLOV from Dinoroseobacter shibae.

Light, oxygen, voltage (LOV) proteins, a ubiquitously distributed class of photoreceptors, regulate a wide variety of light-dependent physiological responses. Because of their modular architecture, LOV domains, i.e., the sensory domains of LOV photoreceptors, have been widely used for the construction of optogenetic tools. We recently described the structure and function of a short LOV protein (DsLOV) from the marine phototropic bacterium Dinoroseobacter shibae, for which, in contrast to other LOV photoreceptors, the dark state represents the physiologically relevant signaling state. Among bacterial LOV photoreceptors, DsLOV possesses an exceptionally fast dark recovery, corroborating its function as a “dark” sensor. To address the mechanistic basis of this unusual characteristic, we performed a comprehensive mutational, kinetic, thermodynamic, and structural characterization of DsLOV. The mechanistic basis of the fast dark recovery of the protein was revealed by mutation of the previously noted uncommon ...