University of Regensburg

CRY4 photomagnetoreception!?

One of the major unanswered questions in biology is how animals navigate over long distances using the Earth magnetic field. Although much effort was made in the last decades to unravel this remarkable feat, the primary sensory mechanism and subsequent signal transduction is still unclear. Currently, Cryptochromes (CRY) are discussed as the most promising photo-magnetoreceptor candidates in animals.[1] In birds three cryptochromes (type II, and IV) are found. Two are involved in the lightindependent regulation of the circadian clock due to the lack of FAD binding,[2] whereas the type IV cryptochrome is proposed to act as the photo-magnetoreceptor, since it shows magneto-sensitivity in the milli tesla magnetic flux densities in vitro. Type II and IV CRYs are also found in amphibians like frogs. In 1987 it was shown that the pigmentation of Xenopus laevis is sensitive to light and external magnetic fields. [3] 

Therefore, we investigated the characteristics of all three cryptochromes from Xenopus laevis by means of stationary and time-resolved absorption spectroscopy as well as theoretical approaches. The results are compared with bird cryptochromes and are discussed in the context of the widely proposed radical pair mechanism.