Fig. 1.

Sequence alignment among (6-4) PHRs and clock CRYs in the α-helical domain, highlighting sequence conservation, functional motifs, and site-directed mutants. Sequence-conserved (white on red) and similar (red on white) residues are boxed. At64PHR secondary structure and amino acid numbering are shown at the top. Yellow circles show residues binding FAD with main and side chains (red and blue rims, respectively). Gray circles show the Trp triad. Squares show mutational sites for CLOCK/BMAL1 repression assays (see Fig. 5).