Evaluation of the steric impact of flavin adenine dinucleotide in Drosophila melanogaster cryptochrome function

One Actor, Multiple Roles: The Performances of Cryptochrome in Drosophila

“…More intriguingly, all such photoreceptor-independent roles of CRY seem to be cell or tissue specific, and different regulating mechanisms might account for the high versatility of its functioning. At least four different tissue-specific regulation mechanisms could make CRY pleiotropy possible: (1) In the clock neurons, the blue light-dependent FAD photoreduction induces conformational changes in the Trp tetrad, which results in the displacement of the CTT from the photolyase homology domain and in consequent protein activation (Zoltowski et al, 2011;Czarna et al, 2013;Levy et al, 2013;Vaidya et al, 2013;Masiero et al, 2014;Lin et al, 2018). (2) In the l-LN v s, lightevoked CRY membrane electrical depolarization involves W420, which is located closest to CRY FAD and is important for CRYmediated depolarization in response not only to UV and blue light but also to red light, at a relatively low intensity (Baik et al, 2019).…”

“…The 542-amino-acid (aa) protein harbors two different domains ( Table 1): an N-terminal photolyase homology region (PHR) and a C-terminus tail (CTT), unique in its sequence, responsible for mediating phototransduction (Busza et al, 2004;Dissel et al, 2004;Hemsley et al, 2007; Figure 1). The CTT forms a helix structure that binds alongside the main body of the PHR domain establishing contacts with the FAD binding pocket, mimicking the damaged DNA photolyase-DNA interaction (Zoltowski et al, 2011;Czarna et al, 2013;Levy et al, 2013;Masiero et al, 2014;Lin et al, 2018). Upon illumination with blue light (440 nm), the CRY FAD cofactor is reduced to the anionic semiquinone (ASQ) state by a fast electron transfer involving four conserved tryptophan residues (W420, W397, W342, and W394).…”

“…Upon illumination with blue light (440 nm), the CRY FAD cofactor is reduced to the anionic semiquinone (ASQ) state by a fast electron transfer involving four conserved tryptophan residues (W420, W397, W342, and W394). FAD photoreduction induces conformational changes in the Trp tetrad, which result in the displacement of the CTT from the PHR domain and consequent protein activation (Zoltowski et al, 2011;Czarna et al, 2013;Levy et al, 2013;Vaidya et al, 2013;Masiero et al, 2014;Lin et al, 2018). However, the Trp-tetrad-dependent photoreduction and circadian photic resetting were suggested to be independent of each other (Ozturk et al, 2014).…”

“…H378 stabilizes the CTT in the resting-state conformation in the dark; light induces a series of conformational changes from nanoseconds to milliseconds that lead to the formation of the final signaling state, which depends on pH and requires uptake of a proton (Berntsson et al, 2019). MD simulations have also suggested for the FAD cofactor roles other than photoreduction and CRY activation: the FAD presence would confer to the receptor a more fluctuation-prone behavior, thus decreasing the amount of necessary light input energy for CRY activation (Masiero et al, 2014). Recent studies performed on a longer timescale have revealed that following photoactivation, FAD is released from the FAD-binding pocket, providing evidence that CRY undergoes an inactivation reaction rather than a photocycle (Kutta et al, 2018), in agreement with the reported irreversible nature of the light-induced conformational changes (Ozturk et al, 2009;Kattnig et al, 2018;Lin et al, 2018).…”

“…The CTT of CRY has been extensively studied, and a combination of in silico analyses and experimental validation has revealed the presence of an intrinsically disordered region containing several interaction motifs that turn this tail into a hot spot for molecular interactions (Hemsley et al, 2007;Mazzotta et al, 2013;Masiero et al, 2014). It can be divided into two subregions: one (493-520 aa) required for the interaction with PER and TIM (Hemsley et al, 2007) and the other (521-542 aa) specifically involved in the light activation of the CRY protein (Rosato et al, 2001;Busza et al, 2004;Dissel et al, 2004).…”