The predominant theory of magnetoreception, the ability of a neuron to sense a magnetic field (MF), focusses on a quantum effect that MF’s have on a radical pair of electrons between Flavin Adenine Dinucleotide (FAD) and Tryptophan residues within the protein CRYPTOCHROME (CRY). The majority of this work has focussed on the canonical theory that most likely underpins the avian magneto-compass.
However, several experimental observations challenge this model including the finding that the C-terminal fragment of Drosophila CRY (DmCRY-CT), which lacks any canonical FAD binding pocket, and human CRY2, which lacks affinity for FAD, are sufficient to render a neuron magnetosensitive. With ever growing exposure to anthropomorphic electromagnetic noise, it is essential that other mechanisms of magnetosensitivity are understood.
Here, we use in silico all-atom molecular dynamic simulations, alongside in vitro and in vivo analyses to reveal the first mechanistic data for a non-canonical mechanism of magnetoreception. We show evidence for the direct electrostatic binding of FAD to the C-terminus DmCRY-CT. FAD binding is required for the transduction of a magnetic signal within cells and initiates the formation of high molecular weight DmCRY-CT oligomers in vitro, which may have implications in the development of magneto-genetic tools. These results provide a plausible mechanistic basis for several experimental observations that have reported non-canonical magnetosensitivity in animals.