Putative blue-light photoreceptors from Arabidopsis thaliana and Sinapis alba with a high degree of sequence homology to DNA photolyase contain the two photolyase cofactors but lack DNA repair activity.

The putative blue-light photoreceptor genes of Arabidopsis thaliana and Sinapis alba (mustard) are highly homologous to the DNA repair genes encoding DNA photolyases. The photoreceptors from both organisms were overexpressed in Escherichia coli, purified, and characterized. The photoreceptors contain two chromophores which were identified as flavin adenine dinucleotide and methenyltetrahydrofolate. This chromophore composition suggests that the blue light photoreceptor may initiate signal transduction by a novel pathway which involves electron transfer. Despite the high degree of sequence identity to and identical chromophore composition with photolyases, neither photoreceptor has any photoreactivating activity.