Max-Planck-Institute for Bioinorganic Chemistry, Mülheim, Germany
Sensing the quality of incident light is of paramount relevance for nearly all organisms. This is especially the case for the blue - near-UV region, as this spectral quality has two sides: it enables for repair of UV-generated DNA damage by photolyases, but it also can generate reactive oxygen species via the involvement of photosensitizer compounds. The most widely spread blue light (BL) sensing photoreceptors in bacteria are the LOV-domain containing proteins (LOV, light, oxygen, voltage). Their function is based on the photochemistry of the flavin mononucleotide (FMN) chromophore that forms upon light excitation a transient covalent bond to the protein. This state is considered the signaling state, as the interaction with the protein generates a biological signal that allows the organisms adapting its lifestyle to the environmental illumination conditions. Signal generation / transmission in many receptors involves the activation of a second protein domain hosting an enzyme function. This naturally occurring function, i.e., the regulation of an enzyme activity by light represents a promising function that finds entrance nowadays also into biotechnological applications, as light activation is non-invasive and can thus be applied even in organisms in which no such photoreceptor is originally found. This is especially interesting when the compound formed by the enzyme induces physiological responses in a given host organism. Both the naturally occurring function of LOV proteins in bacteria as also novel biotechnological applications will be presented.