Comparative Photochemistry of Animal Type 1 and Type 4 Cryptochromes

摘要

ABSTRACT: Cryptochromes (CRYs) are blue-light photoreceptors with known or presumed functions in light-ndependent and light-independent gene regulation in plants and animals. Although the photochemistry ofnplant CRYs has been studied in some detail, the photochemical behavior of animal cryptochromes remainsnpoorly defined in part because it has been difficult to purify animal CRYs with their flavin cofactors. Here wendescribe the purification of type 4 CRYs of zebrafish and chicken as recombinant proteins with full flavinncomplement and compare the spectroscopic properties of type 4 and type 1 CRYs. In addition, we analyzednphotoinduced proteolytic degradation of both types of CRYs in vivo in heterologous systems. We find thatneven though both types of CRYs contain stoichiometric flavin, type 1 CRY is proteolytically degraded by anlight-initiated reaction in Drosophila S2, zebrafish Z3, and human HEK293T cell lines, but zebrafish CRY4n(type 4) is not. In vivo degradation of type 1 CRYs does not require continuous illumination, and a single lightnflash of 1 ms duration leads to degradation of about 80% of Drosophila CRY in 60 min. Finally, wendemonstrate that in contrast to animal type 2 CRYs and Arabidopsis CRY1 neither insect type 1 nor type 4nCRYs have autokinase activities.