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Magnetic sensitivity of cryptochrome 4 from a migratory songbird


Night-migratory songbirds are remarkably proficient navigators1. Flying alone and often over great distances, they use various directional cues including, crucially, a light-dependent magnetic compass2,3. The mechanism of this compass has been suggested to rely on the quantum spin dynamics of photoinduced radical pairs in cryptochrome flavoproteins located in the retinas of the birds4,5,6,7. Here we show that the photochemistry of cryptochrome 4 (CRY4) from the night-migratory European robin (Erithacus rubecula) is magnetically sensitive in vitro, and more so than CRY4 from two non-migratory bird species, chicken (Gallus gallus) and pigeon (Columba livia). Site-specific mutations of ErCRY4 reveal the roles of four successive flavin–tryptophan radical pairs in generating magnetic field effects and in stabilizing potential signalling states in a way that could enable sensing and signalling functions to be independently optimized in night-migratory birds.

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Fig. 1: Purification, electron transfer pathway and photoreduction of European robin CRY4.
Fig. 2: Magnetic field effects on the yields of photoinduced radicals in CRY4 proteins.
Fig. 3: Electron paramagnetic resonance and optical spectroscopy of photoinduced FAD–Trp radical pairs in ErCRY4.
Fig. 4: Reaction scheme and simulated magnetic field effects for ErCRY4.

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The complete set of molecular dynamics simulation and quantum chemistry data (300 GB) can be downloaded from the University of Oldenburg repository: Specific molecular dynamics data can also be obtained directly from I.A.S. on request. Source data are provided with this paper.


  1. Mouritsen, H. Long-distance navigation and magnetoreception in migratory animals. Nature 558, 50–59 (2018).

    Article  ADS  CAS  PubMed  Google Scholar 

  2. Wiltschko, W., Munro, U., Ford, H. & Wiltschko, R. Red-light disrupts magnetic orientation of migratory birds. Nature 364, 525–527 (1993).

    Article  ADS  Google Scholar 

  3. Zapka, M. et al. Visual but not trigeminal mediation of magnetic compass information in a migratory bird. Nature 461, 1274–1277 (2009).

    Article  ADS  CAS  PubMed  Google Scholar 

  4. Hore, P. J. & Mouritsen, H. The radical-pair mechanism of magnetoreception. Annu. Rev. Biophys. 45, 299–344 (2016).

    Article  CAS  PubMed  Google Scholar 

  5. Ritz, T., Adem, S. & Schulten, K. A model for photoreceptor-based magnetoreception in birds. Biophys. J. 78, 707–718 (2000).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. Ritz, T., Thalau, P., Phillips, J. B., Wiltschko, R. & Wiltschko, W. Resonance effects indicate a radical-pair mechanism for avian magnetic compass. Nature 429, 177–180 (2004).

    Article  ADS  CAS  PubMed  Google Scholar 

  7. Engels, S. et al. Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird. Nature 509, 353–356 (2014).

    Article  ADS  CAS  PubMed  Google Scholar 

  8. Steiner, U. E. & Ulrich, T. Magnetic field effects in chemical kinetics and related phenomena. Chem. Rev. 89, 51–147 (1989).

    Article  CAS  Google Scholar 

  9. Maeda, K. et al. Chemical compass model of avian magnetoreception. Nature 453, 387–390 (2008).

    Article  ADS  CAS  PubMed  Google Scholar 

  10. Kerpal, C. et al. Chemical compass behaviour at microtesla magnetic fields strengthens the radical pair hypothesis of avian magnetoreception. Nat. Commun. 10, 3707 (2019).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  11. Giovani, B., Byrdin, M., Ahmad, M. & Brettel, K. Light-induced electron transfer in a cryptochrome blue-light photoreceptor. Nat. Struct. Biol. 10, 489–490 (2003).

    Article  CAS  PubMed  Google Scholar 

  12. Müller, P., Yamamoto, J., Martin, R., Iwai, S. & Brettel, K. Discovery and functional analysis of a 4th electron-transferring tryptophan conserved exclusively in animal cryptochromes and (6-4) photolyases. Chem. Commun. 51, 15502–15505 (2015).

    Article  Google Scholar 

  13. Nohr, D. et al. Determination of radical–radical distances in light-active proteins and their implication for biological magnetoreception. Angew. Chem. Int. Ed. 56, 8550–8554 (2017).

    Article  CAS  Google Scholar 

  14. Nohr, D. et al. Extended electron-transfer pathways in animal cryptochromes mediated by a tetrad of aromatic amino acids. Biophys. J. 111, 301–311 (2016).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  15. Zoltowski, B. D. et al. Chemical and structural analysis of a photoactive vertebrate cryptochrome from pigeon. Proc. Natl Acad. Sci. USA 116, 19449–19457 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  16. Sheppard, D. M. W. et al. Millitesla magnetic field effects on the photocycle of an animal cryptochrome. Sci. Rep. 7, 42228 (2017).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  17. Maeda, K. et al. Magnetically sensitive light-induced reactions in cryptochrome are consistent with its proposed role as a magnetoreceptor. Proc. Natl Acad. Sci. USA 109, 4774–4779 (2012).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  18. Fedele, G., Green, E. W., Rosato, E. & Kyriacou, C. P. An electromagnetic field disrupts negative geotaxis in Drosophila via a CRY-dependent pathway. Nat. Commun. 5, 4391 (2014).

    Article  ADS  CAS  PubMed  Google Scholar 

  19. Gegear, R. J., Casselman, A., Waddell, S. & Reppert, S. M. Cryptochrome mediates light-dependent magnetosensitivity in Drosophila. Nature 454, 1014–1018 (2008).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  20. Hoang, N. et al. Human and Drosophila cryptochromes are light activated by flavin photoreduction in living cells. PLoS Biol. 6, e160 (2008).

    Article  PubMed  PubMed Central  Google Scholar 

  21. Pooam, M. et al. Magnetic sensitivity mediated by the Arabidopsis blue-light receptor cryptochrome occurs during flavin reoxidation in the dark. Planta 249, 319–332 (2019).

    Article  CAS  PubMed  Google Scholar 

  22. Xu, C. X., Lv, Y., Chen, C. F., Zhang, Y. X. & Wei, S. F. Blue light-dependent phosphorylations of cryptochromes are affected by magnetic fields in Arabidopsis. Adv. Space Res. 53, 1118–1124 (2014).

    Article  ADS  CAS  Google Scholar 

  23. Giachello, C. N. G., Scrutton, N. S., Jones, A. R. & Baines, R. A. Magnetic fields modulate blue-light-dependent regulation of neuronal firing by cryptochrome. J. Neurosci. 36, 10742–10749 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  24. Watari, R. et al. Light-dependent structural change of chicken retinal cryptochrome4. J. Biol. Chem. 287, 42634–42641 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  25. Günther, A. et al. Double-cone localization and seasonal expression pattern suggest a role in magnetoreception for European robin cryptochrome 4. Curr. Biol. 28, 211–223.e4 (2018).

    Article  PubMed  Google Scholar 

  26. Nießner, C., Denzau, S., Peichl, L., Wiltschko, W. & Wiltschko, R. Magnetoreception in birds: I. Immunohistochemical studies concerning the cryptochrome cycle. J. Exp. Biol. 217, 4221–4224 (2014).

    Article  PubMed  PubMed Central  Google Scholar 

  27. Nießner, C., Denzau, S., Peichl, L., Wiltschko, W. & Wiltschko, R. Magnetoreception: activation of avian cryptochrome 1a in various light conditions. J. Comp. Physiol. A 204, 977–984 (2018).

    Article  Google Scholar 

  28. Wiltschko, R., Ahmad, M., Nießner, C., Gehring, D. & Wiltschko, W. Light-dependent magnetoreception in birds: the crucial step occurs in the dark. J. R. Soc. Interface 13, 20151010 (2016).

    Article  PubMed  PubMed Central  Google Scholar 

  29. Player, T. C. & Hore, P. J. Viability of superoxide-containing radical pairs as magnetoreceptors. J. Chem. Phys. 151, 225101 (2019).

    Article  ADS  PubMed  Google Scholar 

  30. Müller, P. & Ahmad, M. Light-activated cryptochrome reacts with molecular oxygen to form a flavin–superoxide radical pair consistent with magnetoreception. J. Biol. Chem. 286, 21033–21040 (2011).

    Article  PubMed  PubMed Central  Google Scholar 

  31. Bolte, P. et al. Cryptochrome 1a localisation in light- and dark-adapted retinae of several migratory and non-migratory bird species: no signs of light-dependent activation. Ethol. Ecol. Evol. (2021).

  32. Kutta, R. J., Archipowa, N., Johannissen, L. O., Jones, A. R. & Scrutton, N. S. Vertebrate cryptochromes are vestigial flavoproteins. Sci. Rep. 7, 44906 (2017).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  33. Qin, S. et al. A magnetic protein biocompass. Nat. Mater. 15, 217–226 (2016).

    Article  ADS  CAS  PubMed  Google Scholar 

  34. Maeda, K. et al. Following radical pair reactions in solution: a step change in sensitivity using cavity ring-down detection. J. Am. Chem. Soc. 133, 17807–17815 (2011).

    Article  CAS  PubMed  Google Scholar 

  35. Neil, S. R. T. et al. Broadband cavity-enhanced detection of magnetic field effects in chemical models of a cryptochrome magnetoreceptor. J. Phys. Chem. B 118, 4177–4184 (2014).

    Article  CAS  PubMed  Google Scholar 

  36. Roos, A. & Boron, W. F. Intracellular pH. Physiol. Rev. 61, 296–434 (1981).

    Article  CAS  PubMed  Google Scholar 

  37. Reeves, R. B. The interaction of body temperature and acid–base balance in ectothermic vertebrates. Annu. Rev. Physiol. 39, 559–586 (1977).

    Article  CAS  PubMed  Google Scholar 

  38. Weber, S. et al. Origin of light-induced spin-correlated radical pairs in cryptochrome. J. Phys. Chem. B 114, 14745–14754 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  39. Hochstoeger, T. et al. The biophysical, molecular, and anatomical landscape of pigeon CRY4: a candidate light-based quantal magnetosensor. Sci. Adv. 6, eabb9110 (2020).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  40. Kattnig, D. R., Solov’yov, I. A. & Hore, P. J. Electron spin relaxation in cryptochrome-based magnetoreception. Phys. Chem. Chem. Phys. 18, 12443–12456 (2016).

    Article  CAS  PubMed  Google Scholar 

  41. Efimova, O. & Hore, P. J. Role of exchange and dipolar interactions in the radical pair model of the avian magnetic compass. Biophys. J. 94, 1565–1574 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  42. Timmel, C. R., Till, U., Brocklehurst, B., McLauchlan, K. A. & Hore, P. J. Effects of weak magnetic fields on free radical recombination reactions. Mol. Phys. 95, 71–89 (1998).

    Article  ADS  CAS  Google Scholar 

  43. Worster, S., Mouritsen, H. & Hore, P. J. A light-dependent magnetoreception mechanism insensitive to light intensity and polarization. J. R. Soc. Interface 14, 20170405 (2017).

    Article  PubMed  PubMed Central  Google Scholar 

  44. Kattnig, D. R., Sowa, J. K., Solov’yov, I. A. & Hore, P. J. Electron spin relaxation can enhance the performance of a cryptochrome-based magnetic compass sensor. New J. Phys. 18, 063007 (2016).

    Article  ADS  Google Scholar 

  45. Wu, H., Scholten, A., Einwich, A., Mouritsen, H. & Koch, K. W. Protein–protein interaction of the putative magnetoreceptor cryptochrome 4 expressed in the avian retina. Sci. Rep. 10, 7364 (2020).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

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This work was supported by the Air Force Office of Scientific Research (Air Force Materiel Command, USAF award no. FA9550-14-1-0095, to P.J.H., H.M., C.R.T., S.R.M. and K.-W.K.); by the European Research Council (under the European Union’s Horizon 2020 research and innovation programme, grant agreement no. 810002, Synergy Grant: ‘QuantumBirds’, awarded to P.J.H. and H.M.); by the Office of Naval Research Global, award no. N62909-19-1-2045, to P.J.H., C.R.T. and S.R.M.; by the Deutsche Forschungsgemeinschaft (SFB 1372, ‘Magnetoreception and navigation in vertebrates’, project number: 395940726 to H.M., K.-W.K., I.A.S. and P.J.H., and GRK 1885, ‘Molecular basis of sensory biology’ to K.-W.K., I.A.S. and H.M.); by a DAAD (German Academic Exchange Service, Graduate School Scholarship Programme, ID 57395813) stipend to J.X.; by funding for G.M. from the SCG Innovation Fund; by the Electromagnetic Fields Biological Research Trust (to P.J.H., C.R.T. and S.R.M.); by the National Natural Science Foundation of China, grant no. 31640001, and the Presidential Foundation of Hefei Institutes of Physical Science, Chinese Academy of Sciences, grant no. BJZX201901 (to C.X.); and by the Lundbeck Foundation, the Danish Councils for Independent Research, and the Volkswagen Foundation (to I.A.S.). V.D. is grateful to the Clarendon Fund, University of Oxford. M.J.G. thanks the Biotechnology and Biological Sciences Research Council, grant number BB/M011224/1 and the Clarendon Fund. We acknowledge use of the Advanced Research Computing (ARC) facility of the University of Oxford. J.S.T. is an Investigator and Y.C. is a Research Specialist in the Howard Hughes Medical Institute. I.A.S. is grateful to the DeiC National HPC Center, University of Southern Denmark for computational resources. We thank B. Grünberg, I. Fomins, A. Günther and A. Einwich for laboratory assistance and for providing protein sequence information. J.X. thanks Y. Tan for training in protein expression and purification. We thank S. Chandler for mass spectrometry, S. Y. Wong for assistance with spin dynamics calculations, and W. Myers (CAESR, Engineering and Physical Sciences Research Council, grant no. EP/L011972/1) for obtaining a threefold improvement in the time-resolved electron paramagnetic resonance signal. We are grateful to the staff of the mechanical and electronic workshops in the Oxford Chemistry Department and at the University of Oldenburg.

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Authors and Affiliations



J.X., L.E.J., T.Z., M.K., K.B.H., S.R. and M.J.G. made particularly important experimental contributions. J.X. cloned wild-type ErCRY4 and all the mutants and developed the protocols for expression and purification of the proteins with FAD bound. J.X. and J.S. produced the protein samples. L.E.J. developed the continuous illumination experiment for studying photoreduction and the picosecond transient absorption experiment for measuring magnetic field effects, and recorded and interpreted data. T.Z. and M.J.G. developed the CRDS experiment for measuring magnetic field effects and recorded and interpreted data. M.K. developed the broadband cavity-enhanced absorption spectroscopy experiment for measuring magnetic field effects and recorded and interpreted data. S.R. and S.W. recorded and interpreted the EPR data. K.B.H. participated in all five of the above experiments and recorded and interpreted spectroscopic data. J.F., with K.B.H., recorded and interpreted some of the transient absorption data and all of the re-oxidation data. M.K. helped with the global analysis of the re-oxidation data. M.J.G., V.D., J.R.W. and P.D.F.M. made spectroscopic measurements of magnetic field effects. D.J.C.S. helped to develop the picosecond TA apparatus. J.L. and Y.W. performed spin dynamics calculations. T.L.P. and G.M. reproduced and helped to interpret the EPR data. A.S.G. recorded and interpreted mass spectra. M.B. expressed and purified chicken CRY4. M.H., S.H., G.D. and S.J.K. expressed and purified some of the ErCRY4 protein samples. Y.C., J.S.T. and J.X. expressed and purified pigeon CRY4. H.Y., H.W., K.-W.K., R.B. and C.X. provided advice on protein expression. I.A.S. performed molecular dynamics simulations and provided advice on cryptochrome structure and dynamics. L.E.J. had oversight of the organization and administration of the optical spectroscopy measurements. P.J.H., H.M., C.R.T. and S.R.M. conceived the study. P.J.H., H.M., C.R.T., S.R.M. and C.X. supervised the work. P.J.H. and H.M. wrote the manuscript, and all authors commented on the manuscript.

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Correspondence to Ilia A. Solov’yov, Can Xie, Stuart R. Mackenzie, Christiane R. Timmel, Henrik Mouritsen or P. J. Hore.

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Xu, J., Jarocha, L.E., Zollitsch, T. et al. Magnetic sensitivity of cryptochrome 4 from a migratory songbird. Nature 594, 535–540 (2021).

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