Phytochromes are modular, red light-sensing photoreceptors found in plants and bacteria. We have previously revealed how incident light induces a hierarchy of structural changes that lead to a large opening of the phytochrome photosensory module. This movement changes the activity of the output biochemical activity of phytochrome and its interactions with other proteins. However, the structural details of these changes still remain unclear. Our aim is to uncover how phytochromes function: How small light-induced changes in the biliverdin chromophore are propagated and amplified to a large opening of the phytochrome photosensory module? How the structural changes in the photosensory module affect the activity of the effector module and its binding to other proteins?
Optogenetics is a field of research where protein complexes, and hence cellular processes, are controlled with light. For this, photoreceptor proteins are rationally engineered as optogenetic tools by fusing them to a new effector part. Currently most of these tools are limited because they sense blue light, are nonreversible, or require external chromophores. Bacterial phytochromes offer a solution for these limitations as they sense red light, are reversible, and use a chromophore native to mammalian cells. These unique properties make them excellent optogenetic tools. Our aim is to generate new phytochrome-based applications. These tools will be based on light-induced changes of the phytochrome (e.g., dimerization, structural change), which will coupled to the function of a new effector protein.
