photolyaselike

Photolyaselike refers to proteins that are homologous to photolyases but may differ in activity or function from classic DNA repair enzymes. They belong to the photolyase/cryptochrome (PHR) superfamily and typically share the photolyase homology region (PHR). Many photolyaselike proteins bind a flavin adenine dinucleotide (FAD) cofactor and, in some cases, antenna chromophores such as methenyltetrahydrofolate (MTHF) or related compounds, which extend their light-absorption range.

Functions and roles vary among photolyaselike proteins. Traditional photolyases repair UV-induced DNA damage in a blue-light-dependent reaction, restoring pyrimidine dimers. In contrast, many photolyaselike members act as blue-light receptors that regulate circadian rhythms, development, and gene expression in plants, animals, and microbes. Cryptochromes and Cry-DASH proteins are prominent examples; cryptochromes are central to clock entrainment in diverse organisms, while Cry-DASH proteins are implicated in light sensing with variable DNA repair activity across species.

Structure and mechanism are characteristic of the family but with functional diversity. Members typically feature a conserved PHR domain responsible for flavin binding and light-driven chemistry, plus additional regions that influence signaling or repair activity. In photoreceptors, light-induced conformational changes propagate signals to transcriptional networks or clock machinery, whereas in repair-competent photolyases, electron transfer from excited FAD to the DNA lesion mediates repair.

Evolution and classification reflect diversification from a photolyase ancestor. The photolyaselike group includes active photolyases and various cryptochrome subfamilies; their study informs understanding of light perception, genome maintenance, and applications in optogenetics and plant biology.