Formation and function of flavin anion radical in cryptochrome 1 blue-light photoreceptor of monarch butterfly

Sang Hun Song, Nuri Öztürk, Tracy R. Denaro, N. Özlem Arat, Ya-Ting Kao, Haisun Zhu, Dongping Zhong, Steven M. Reppert, Aziz Sancar*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


The monarch butterfly (Danaus plexippus) cryptochrome 1 (DpCry1) belongs in the class of photosensitive insect cryptochromes. Here we purified DpCry1 expressed in a bacterial host and obtained the protein with a stoichiometric amount of the flavin cofactor in the two-electron oxidized, FADox, form. Exposure of the purified protein to light converts the FADox to the FAD.- flavin anion radical by intraprotein electron transfer from a Trp residue in the apoenzyme. To test whether this novel photoreduction reaction is part of the DpCry1 physiological photocycle, we mutated the Trp residue that acts as the ultimate electron donor in flavin photoreduction. The mutation, W328F, blocked the photoreduction entirely but had no measurable effect on the light-induced degradation of DpCry1 in vivo. In light of this finding and the recently published action spectrum of this class of Crys, we conclude that DpCry1 and similar insect cryptochromes do not contain flavin in the FADox form in vivo and that, most likely, the FADoxhv FAD.- photoreduction reaction is not part of the insect cryptochrome photoreaction that results in proteolytic degradation of the photopigment.

Original languageEnglish
Pages (from-to)17608-17612
Number of pages5
JournalJournal of Biological Chemistry
Issue number24
StatePublished - 15 Jun 2007

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