Structural biology of DNA photolyases and cryptochromes.

Photolyases repair cytotoxic and mutagenic UV-induced photolesions in DNA by using an amazing light-dependent repair mechanism. It involves light absorption, electron transfer from an excited reduced and deprotonated FADH(-) to the flipped-out photolesion, followed by the fragmentation of the photolesions. Cryptochromes are highly related proteins that no longer repair damaged DNA, but function as photoreceptors. They feature strikingly similar protein architectures to photolyases and contain an FAD cofactor as well. However, cryptochromes possess an additional signal-transmitting domain, attached either to the N-termini or C-termini. Recently, the field of photorepair and blue-light photoperception has experienced significant progress particularly in structural biology, which is summarized in this review. Today, crystal structures of many family members are known and most recently even complexes of photolyases and DASH-type cryptochrome bound to their DNA substrates became available providing insight into the critical electron and energy transfer reactions that enable genome repair.