Solovyov, I. A. | Search bioRxiv

bioRxiv2025

A Charge-reversal Point Mutation Completely Depletes Flavin Chromophore from European Robin Cryptochrome 4a Protein

Cryptochrome 4a (Cry4a) is a magnetically sensitive protein that could enable night-migratory birds to sense the geomagnetic field for navigation. The key to the protein magnetic sensitivity is the flavin adenine dinucleotide (FAD) cofactor, which initiates the electron transfer within the protein leading to a spin-correlated radical pair. De-spite its importance, the mechanism of FAD binding in avian Cry4a proteins remains unclear. Here we show that point mutagenesis of positively charged arginine residue at position 356 to negatively charged glutamic acid completely depletes FAD binding from European robin (Erithacus rubecula) Cry4a. The result indicates that electrostatic in-teractions constitute the primary driving force that enables FAD binding in European robin Cry4a. The finding provides new structural insight into the molecular basis of FAD binding in Cry4 and advances our understanding on the biophysical underpinnings of bird magnetoreception. Table of Contents Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/690116v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@93344forg.highwire.dtl.DTLVardef@4f642corg.highwire.dtl.DTLVardef@39912corg.highwire.dtl.DTLVardef@169e1de_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2023

A marine cryptochrome with an inverse photo-oligomerization mechanism

Cryptochromes (CRYs) are a structurally conserved but functionally diverse family of proteins that can confer unique sensory properties to organisms. In the marine bristle worm Platynereis dumerilii, its light receptive cryptochrome L-CRY (PdLCry) allows the animal to discriminate between sunlight and moonlight, an important requirement for synchronizing its lunar cycle-dependent mass spawning. Using cryo-electron microscopy, we show that in the dark, PdLCry adopts a dimer arrangement observed neither in plant nor insect CRYs. Intense illumination disassembles the dimer into monomers. Structural and functional data suggest a mechanistic coupling between the light-sensing flavin adenine dinucleotide chromophore, the dimer interface, and the C-terminal tail helix, with a likely involvement of the phosphate binding loop. Taken together, our work establishes PdLCry as a CRY protein with inverse photo-oligomerization with respect to plant CRYs, and provides molecular insights into how this protein might help discriminating the different light intensities associated with sunlight and moonlight.

biochemistry↗