title: Magnetoreception: activated cryptochrome 1a concurs with magnetic orientation in birds.
abstract: The radical pair model proposes that the avian magnetic compass is based on radical pair processes in the eye, with cryptochrome, a flavoprotein, suggested as receptor molecule. Cryptochrome 1a (Cry1a) is localized at the discs of the outer segments of the UV/violet cones of European robins and chickens. Here, we show the activation characteristics of a bird cryptochrome in vivo under natural conditions. We exposed chickens for 30 min to different light regimes and analysed the amount of Cry1a labelled with an antiserum against an epitope at the C-terminus of this protein. The staining after exposure to sunlight and to darkness indicated that the antiserum labels only an illuminated, activated form of Cry1a. Exposure to narrow-bandwidth lights of various wavelengths revealed activated Cry1a at UV, blue and turquoise light. With green and yellow, the amount of activated Cry1a was reduced, and with red, as in the dark, no activated Cry1a was labelled. Activated Cry1a is thus found at all those wavelengths at which birds can orient using their magnetic inclination compass, supporting the role of Cry1a as receptor molecule. The observation that activated Cry1a and well-oriented behaviour occur at 565 nm green light, a wavelength not absorbed by the fully oxidized form of cryptochrome, suggests that a state other than the previously suggested Trp/FAD radical pair formed during photoreduction is crucial for detecting magnetic directions.
authors: FB Biowissenschaften, J.W. Goethe-Universität Frankfurt, Siesmayerstrasse 70, 60054 Frankfurt am Main, Germany.
authors: Christine
authors: C
authors: Nießner
authors: Susanne
authors: S
authors: Denzau
authors: Katrin
authors: K
authors: Stapput
authors: Margaret
authors: M
authors: Ahmad
authors: Leo
authors: L
authors: Peichl
authors: Wolfgang
authors: W
authors: Wiltschko
authors: Roswitha
authors: R
authors: Wiltschko
mesh_terms: D000818:Animals; D002645:Chickens / Q000378:metabolism*; D056931:Cryptochromes / Q000502:physiology*; D060526:Magnetic Fields; D009949:Orientation / Q000502:physiology*; D010084:Oxidation-Reduction / Q000528:radiation effects; D055668:Photochemical Processes / Q000528:radiation effects; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism; D020308:Songbirds / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D014466:Ultraviolet Rays
chemical_list: D056931:Cryptochromes
keywords: conformational change; cryptochrome 1a; flavin cycle; magnetic compass; photoreceptor
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