PUTATIVE HUMAN BLUE-LIGHT PHOTORECEPTORS HCRY1 AND HCRY2 ARE FLAVOPROTEINS

Recently, a human cDNA clone with high sequence homology to the photol yase/blue-light photoreceptor family was identified. The putative prot ein encoded by this gene exhibited a strikingly high (48% identity) de gree of homology to the Drosophila melanogaster (6-4) photolyase [Todo et al. (1996) Science 272, 109-112]. We have now identified a second human gene whose amino acid sequence displays 73% identity to the firs t one and have named the two genes CRY1 and CRY2, respectively. The co rresponding proteins hCRY1 and hCRY2 were purified and characterized a s maltose-binding fusion proteins. Similar to other members of the pho tolyase/blue-light photoreceptor family, both proteins were found to c ontain FAD and a pterin cofactor. Like the plant blue-light photorecep tors, both hCRY1 and hCRY2 lacked photolyase activity on the cyclobuta ne pyrimidine dimer and the (6-4) photoproduct. We conclude that these newly discovered members of the photolyase/photoreceptor family are n ot photolyases and instead may function as blue-light photoreceptors i n humans.