The photolyase/cryptochrome family consists of flavoproteins that perform
various functions using blue-light photons as an energie source. It is present
in all three domains of life, that is, archaea, eubacteria, and eukaryotes,
and hence has arisen very early during evolution to protect genomes against
the genotoxic effects of ultraviolet light originating from the sun. The
photolyase/cryptochrome family is divided into two major groups: photolyases
and cryptochromes. Photolyases (see <PDOC00331> and <PDOC00832>) repair
cytotoxic and mutagenic UV-induced photolesions in DNA in many species from
bacteria to plants and animals by using a light-dependent repair mechanism. It
involves light absorption, electron transfer from an excited reduced and
deprotanated FADH(-) to the flipped-out photolesion, followed by the
fragmentation of the photolesions. Cryptochromes are highly related proteins
that generally no longer repair damaged DNA, but function as photoreceptors.
Cryptochromes regulate growth and development in plants and the circadian
clock in animals [1,2,3,4,5,6,7].
Both photolyases and cryptochromes have a bilobal architecture consisting of
two domains: an N-terminal α/β domain that may contain a light-harvesting chromophore to additionally broaden their activity spectra and a C-terminal α-helical catalytic domain comprising the light-sensitive FAD
cofactor. Diverse classes of antenna chromophores likes 5,10-methenyltetrahydrofolate (MTHF), 8-hydroxydeazaflavin, FMN or FAD have been
identified in some photolyase/cryptochrome to broaden their activity spectra,
whereas many others apparently lack any bound antenna chromophores.
The photolyase/cryptochrome α/β domain adopts a dinucleotide binding
fold with a five-stranded parallel β sheet flanked on both sides by α
helices (see <PDB:1NP7>) [1,5].
Some proteins known to contain a photolyase/cryptochrome α/β domain are
- CPD photolyases, known as pyrimidine photolyase, repair cyclobutane
pyrimidine dimer (CPD).
- (6-4) photolyases, repair (6-4) pyrimidine-pyrimidone photoproducts (6-
- cryptochromes-DASH (CRY-DASH), photolyases with high specificity for CPDs
in single-stranded DNA.
- cryptochromes, act as blue-light photoreceptors and exert various
The profile we developed covers the entire photolyase/cryptochrome α/β
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