Authors: Nuri Ozturk, Christopher Selby, Dongping Zhong, Aziz Sancar
Title: Mechanism of Photosignaling by Drosophila Cryptochrome:Role of the Redox Status of the Flavin Chromophore"
Summary: Can both redox forms of the Drosophila circadian rhythm photoreceptor carry out signaling?
The fruit fly has one photoreceptor that plays an essential role in circadian rhythms. The flavin cofactor of the photoreceptor cryptochrome (CRY) undergoes redox cycles but it’s unclear whether the redox status of dCRY resets the Drosophila circadian clock. In this Paper of the Week, a team led by Aziz Sancar at the University of North Carolina School of Medicine analyzed the interactions between a tryptophan triad in dCRY that is important for redox cycles of the flavin cofactor and a fourth tryptophan residue, Trp 536, which is thought to be a potential electron donor. They demonstrated both the reduced and oxidized forms of dCRY were capable of phototransduction, which meant that the tryptophan triad and Trp 536 had no effect on the photoreceptor’s function. The investigators also showed that flavin reduction was not necessary for a conformational change for dCRY signaling; this finding contradicts conclusions from other studies that say the flavin redox state affects dCRY’s conformational rearrangement. The authors say, “We conclude that both oxidized and reduced forms of dCRY are capable of photosignaling.”
Reference: Ozturk N, Selby CP, Zhong D, Sancar A. (2014) Mechanism of Photosignaling by Drosophila Cryptochrome: Role of the Redox Status of the Flavin Chromophore. J Biol Chem. 289: 4634-4642
Link to JBC website: http://www.jbc.org/content/289/8/4634