Formation and function of flavin anion radical in cryptochrome 1 blue-light photoreceptor of monarch butterfly.
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, FAD(ox), form. Exposure of the purified protein to light converts the FAD(ox) 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 FAD(ox) form in vivo and that, most likely, the [see text] photoreduction reaction is not part of the insect cryptochrome photoreaction that results in proteolytic degradation of the photopigment.
Song
Sang-Hun
SH
Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
Oztürk
Nuri
N
Denaro
Tracy R
TR
Arat
N Ozlem
NO
Kao
Ya-Ting
YT
Zhu
Haisun
H
Zhong
Dongping
D
Reppert
Steven M
SM
Sancar
Aziz
A
D000818:Animals; D000838:Anions / Q000737:chemistry / Q000378:metabolism*; D002080:Butterflies; D056931:Cryptochromes; D005415:Flavins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005420:Flavoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010777:Photochemistry; D017956:Photoreceptor Cells, Invertebrate / Q000737:chemistry / Q000502:physiology
D000838:Anions; D056931:Cryptochromes; D005415:Flavins; D005420:Flavoproteins; D019476:Insect Proteins