One More for Light-triggered Conformational Changes in Cryptochromes: CryP from Phaeodactylum tricornutum.

[Display omitted] • CryP-like cryptochromes are a novel subfamily of the PCSf. • CryP-like cryptochromes harbor a unique β-hairpin motif at the C-terminus. • The CTE with its β-hairpin undergoes conformational change in the semichinoid state. • The CTE is found to interact with the MMWQN motif of the photolyase-homology region. • CryP-like cryptochromes occur in algae, diatoms and aquatic chordata. Cryptochromes are a ubiquitously occurring class of photoreceptors. Together with photolyases, they form the Photolyase Cryptochrome Superfamily (PCSf) by sharing a common protein architecture and binding mode of the FAD chromophore. Despite these similarities, PCSf members exert different functions. Photolyases repair UV-induced DNA damage by photocatalytically driven electron transfer between FADH¯ and the DNA lesion, whereas cryptochromes are light-dependent signaling molecules and trigger various biological processes by photoconversion of their FAD redox and charge states. Given that most cryptochromes possess a C-terminal extension (CTE) of varying length, the functions of their CTE have not yet been fully elucidated and are hence highly debated. In this study, the role of the CTE was investigated for a novel subclass of the PCSf, the CryP-like cryptochromes, by hydrogen/deuterium exchange and mass-spectrometric analysis. Striking differences in the relative deuterium uptake were observed in different redox states of CryP from the diatom Phaeodactylum tricornutum. Based on these measurements we propose a model for light-triggered conformational changes in CryP-like cryptochromes that differs from other known cryptochrome families like the insect or plant cryptochromes. [ABSTRACT FROM AUTHOR]