PhotoGene

Photoreceptor proteins regulate adaptation of living organisms to light. A class recently discovered uses a vitamin B12 derivative to sense green light and regulate the biosynthesis of carotenoids, which protect against photo-oxidative damage. CarH is a prototype of this class. Its sophisticated machinery has been proposed as a promising optogenetic tool, yet its design and optimization requires detailed knowledge of the molecular mechanism in real time. Structural and spectroscopic data on CarH suggest a complex photochemical and structural pathway in the picosecond-to-second time scale connecting photon absorption to major quaternary changes. We propose to provide a molecular description of CarH gene regulation mechanism by using the new tools for structural biology available at advanced X-ray sources (synchrotrons and free electron lasers). The results will enable to uncover the structural basis of light-dependent gene regulation by one of Nature’s most complex metallo-cofactors.