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Abstract:
Cryptochromes (Cry) have been suggested to form the basis of light-dependent magnetic compass orientation in birds.
However, to function as magnetic compass sensors, the cryptochromes of migratory birds must possess a number of key
biophysical characteristics. Most importantly, absorption of blue light must produce radical pairs with lifetimes longer than
about a microsecond. Cryptochrome 1a (gwCry1a) and the photolyase-homology-region of Cry1 (gwCry1-PHR) from the
migratory garden warbler were recombinantly expressed and purified from a baculovirus/Sf9 cell expression system. Transient
absorption measurements show that these flavoproteins are indeed excited by light in the blue spectral range leading to the
formation of radicals with millisecond lifetimes. These biophysical characteristics suggest that gwCry1a is ideally suited as
a primary light-mediated, radical-pair-based magnetic compass receptor.
