<p>DNA photolyases are enzymes that bind to DNA containing pyrimidine dimers:on absorption of visible light, they catalyse dimer splitting into theconstituent monomers, a process called photoreactivation [<cite idref="PUB00002404"/>]. This is a DNArepair mechanism, repairing mismatched pyrimidine dimers induced byexposure to ultra-violet light [<cite idref="PUB00001750"/>]. The precise mechanisms involved insubstrate binding, conversion of light energy to the mechanical energyneeded to rupture the cyclobutane ring, and subsequent release of theproduct are uncertain [<cite idref="PUB00002404"/>]. Analysis of DNA lyases has revealed the presenceof an intrinsic chromophore, all monomers containing a reduced FAD moiety,and, in addition, either a reduced pterin or 8-hydroxy-5-diazaflavin as asecond chromophore [<cite idref="PUB00001750"/>, <cite idref="PUB00002622"/>]. Either chromophore may act as the primary photonacceptor, peak absorptions occurring in the blue region of the spectrumand in the UV-B region, at a wavelength around 290nm [<cite idref="PUB00002622"/>].</p> <p>This domain binds a light harvesting cofactor.</p> DNA photolyase, N-terminal