Energy and electron transfer processes in flavoprotein-mediated DNA repair

The flavin photoenzyme, DNA photolyase, utilizes a photon to repair the main damage to DNA (pyrimidine dimers) caused by UV light. DNA photolyases are monomeric flavoproteins that bind to the cis-syn-pyrimidine dimer in DNA in a light-independent step, forming a stable enzyme-substrate complex. This complex absorbs a photon, leading to electron transfer to the pyrimidine dimer, producing an unstable cyclobutane radical anion and thereby initiating bond cleavage in the dimer. The mechanism and energetics involved in the action of this remarkable enzyme are reviewed.