Fig. 16

a CRY1-PHR structure (PDB 1U3D) with helices in cyan, β-strands in red, FAD cofactor in yellow, and AMPPNP (ATP analogue) in green. b electrostatic potential in CRY1-PHR and E. coli DNA photolyase (PDB 1DNP). Surface areas colored red and blue represent negative and positive electrostatic potential, respectively. c dCRY (PDB 4JZY) and d 6-4 dPL (PDB 3CVU). The C-terminal tail of dCRY (orange) replaces the DNA substrate in the DNA-binding cleft of dPL. The N-terminal α/β domain (blue) is connected to the C-terminal helical domain (yellow) through a linker (gray). FAD cofactor is in green. e Structural comparison of dCRY (blue; PDB 4JZY) with dCRY (beige; PDB 3TVS, initial structure; 4GU5, updated) [308, 309]. Significant changes are in the regulatory tail and adjacent loops. f Structural comparison of mCRY1 (pink; PDB 4K0R) with the dCRY (cyan; PDB 4JZY) regulatory tail and adjacent loops depicting the changes. Conserved Phe (Phe428_dCRY and Phe405_mCRY1) depicted that facilitates C-terminal lid movement. g dCRY photoactivation mechanism: Trp342, Trp397, and Trp290 form the classic Trp eˉ transfer cascade. Structural analysis suggest the involvement of the eˉ rich sulfur loop (Met331 and Cys337), the tail connector loop (Cys523), and Cys416, which are in close proximity to the Trp cascade in the gating of eˉs via the cascade. h Comparison of the FAD binding pocket of dCRY (cyan) and mCRY1 (pink). Asp387_mCRY1 occupies the binding pocket. The mCRY1 residues (His355 and Gln289), corresponding to His 378 and Gln311 in dCRY, at the pocket entrance are rotated to "clash" with the FAD moiety. Gly250_mCRY1 and His224_mCRY1 superimpose Ser265_dCRY and Arg237_dCRY, respectively. i Crystal structure of the complex (PDB 4I6J) between mCRY2 (yellow), Fbxl3 (orange), and Skp1 (green). The numbers 1, 8, and 12 display the position of the respective leucine rich repeats (LRR) present in Fbxl3