Photolyase and cryptochrome comprise a family of structurally related blue-light photoreceptors. Photolyase repairs UV damaged DNA and cryptochromes mediate a variety of growth and adaptive responses. In this study, three genes, phr, cry1, and cry2, belonging to the photolyase/cryptochrome blue-light photoreceptor family in the V. cholerae genome were biochemically and genetically characterized. All three proteins contained the folate and flavin cofactors. One of these proteins, VcPhr, was found to be a CPD photolyase belonging the Class I photolyases. VcCry1 was found to have a small amount of CPD photolyase activity and belongs to the DASH subfamily. VcCry2 belongs to the DASH-related subfamily. Additionally, I present evidence of a new class of CPD photolyases, Class III photolyases. I have also performed a thorough phylogenetic analysis of the superfamily and have identified conserved motifs unique to individual subclasses and the tertiary location of the conserved regions. I have proposed reclassifying DASH cryptochromes as a novel class of photolyases. Also, presented is the homo- and heterodimerization of vertebrate cryptochromes. Additionally the ancient origins of vertebrate-like cryptochromes were traced back to over one billion years ago.
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