Psychoanalysis

Cryptochrome

Psychology

Chemistry

Photochemistry

Fluorescence

Quantum yield

Vertebrate

Biochemistry

Physics

Triad (sociology)

Circadian clock

Biology

Gene

Optics

Biophysics

Blue light

Quantum mechanics

Magnetoreception

Magnetic field

Earth's magnetic field

Residue (chemistry)

Proceedings of the National Academy of Sciences

Computational and biochemical studies implicate the blue-light sensor cryptochrome (CRY) as an endogenous light-dependent magnetosensor enabling migratory birds to navigate using the Earth's magnetic field. Validation of such a mechanism has been hampered by the absence of structures of vertebrate CRYs that have functional photochemistry. Here we present crystal structures of Columba livia (pigeon) CRY4 that reveal evolutionarily conserved modifications to a sequence of Trp residues (Trp-triad) required for CRY photoreduction. In ClCRY4, the Trp-triad chain is extended to include a fourth Trp (W369) and a Tyr (Y319) residue at the protein surface that imparts an unusually high quantum yield of photoreduction. These results are consistent with observations of night migratory behavior in animals at low light levels and could have implications for photochemical pathways allowing magnetosensing.

Chemical and structural analysis of a photoactive vertebrate cryptochrome from pigeon