InterPro domain: IPR036134

This entry represents a multi-helical domain, composed of two alpha subdomains, found in the C terminus of the cryptochrome proteins and DNA photolyases. It acts as a FAD-binding domain [ 1 ].

The cryptochrome and photolyase families consist of structurally related flavin adenine dinucleotide (FAD) proteins that use the absorption of blue light to accomplish different tasks. The photolyasess use the blue light for light-driven electron transfer to repair UV-damaged DNA, while the cryptochromes are blue-light photoreceptors involved in the circadian clock for plants and animals [ 2 , 3 ].

DNA photolyases are DNA repair enzymes that repair mismatched pyrimidine dimers induced by exposure to ultra-violet light. They bind to UV-damaged DNA containing pyrimidine dimers and, upon absorbing a near-UV photon (300 to 500 nm), they catalyse dimer splitting, breaking the cyclobutane ring joining the two pyrimidines of the dimer so as to split them into the constituent monomers; this process is called photoreactivation. DNA photolyases require two choromophore-cofactors for their activity. All monomers contain a reduced FAD moiety, and, in addition, either a reduced pterin or 8-hydroxy-5-diazaflavin as a second chromophore. Either chromophore may act as the primary photon acceptor, peak absorptions occurring in the blue region of the spectrum and in the UV-B region, at a wavelength around 290nm [ 4 , 5 ].

1. Identification of a new cryptochrome class. Structure, function, and evolution. Mol. Cell 11, 59-67
2. Binding of Substrate Locks the Electrochemistry of CRY-DASH into DNA Repair. Biochemistry 54, 2802-5
3. Evolutionary History of the Photolyase/Cryptochrome Superfamily in Eukaryotes. PLoS ONE 10, e0135940
4. Crystal structure of DNA photolyase from Escherichia coli. Science 268, 1866-72
5. DNA apophotolyase from Anacystis nidulans: 1.8 A structure, 8-HDF reconstitution and X-ray-induced FAD reduction. Acta Crystallogr. D Biol. Crystallogr. 60, 1205-13