A Topologically Distinct Class Of Photolyases Specific For Uv Lesions Within Single-Stranded Dna

Photolyases are ubiquitously occurring flavoproteins for catalyzing photo repair of UV-induced DNA damages. All photolyases described so far have a bilobal architecture with a C-terminal domain comprising flavin adenine dinucleotide (FAD) as catalytic cofactor and an N-terminal domain capable of harboring an additional antenna chromophore. Using sequence-similarity network analysis we discovered a novel subgroup of the photolyase/cryptochrome superfamily (PCSf), the NewPHLs. NewPHL occur in bacteria and have an inverted topology with an N-terminal catalytic domain and a C-terminal domain for sealing the FAD binding site from solvent access. By characterizing two NewPHL we show a photo-chemistry characteristic of other PCSf members as well as light-dependent repair of CPD lesions. Given their common specificity towards single-stranded DNA many bacterial species use NewPHL as a substitute for DASH-type photolyases. Given their simplified architecture and function we suggest that New-PHL are close to the evolutionary origin of the PCSf.