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. 2014 Jan 24;4:3845. doi: 10.1038/srep03845

Figure 1. Electron and proton transfers in cryptochrome.

Figure 1

Shown is the flavin cofactor, the tryptophan triad (W400, W377, W324) and the D396 residue forming the active site of cryptochrome-1 from Arabidopsis thaliana. Electron (red) and proton (green) transfer processes that likely govern cryptochrome activation are presented by arrows. The three electron transfers W400 → flavin, W377 → W400·+, and W324 → W377·+ are labeled I, II, and III, respectively. Electron transfer following flavin photo-excitation leads to a radical pair state of cryptochrome: transfer I to [FAD·− + W400·+] with the averaged pair separation of 7.4 Å, sequential transfer I + II to [FAD·− + W377·+] with pair separation of 12.2 Å, sequential transfer I + II + III to [FAD·− + W324·+] with pair separation of 18.2 Å.