MAS NMR-based studies of phytochrome intramolecular function and signalling

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Phytochromes are photoreceptor molecules widely used in nature to perceive the light environment - for example inducing germination, flowering etc. in plants. We have successfully applied solid-state NMR methods to the cyanobacterial phytochrome Cph1 to find out how phytochromes work. We propose to study how photons de/active the molecule from the primary photoreaction through the protein, eventually to regulate its biochemical activity in the cell. Amino acid types and/or the chromophore will be 13C/15N-labelled pairwise so that interactions and light-dependent changes can be studied throughout the protein. To this end we will also develop methods to allow interatomic distances to be measured accurately. Using in situ irradiation and freeze-trapping we will also study intermediates, deepening our understanding of the underlying the photoreaction per se and the ensuing intramolecular signal transduction mechanism. We will also extend our studies to include specific mutants, allowing us to investigate the mechanism experimentally. We will also study other phytochromes, including those from plants themselves. The information gained will be relevant to the phytochrome photoreceptor family but also to related regulatory molecules, for example the sensory kinases used by microorganisms including pathogens to perceive and respond to their environment.