ENERGY AND ELECTRON-TRANSFER PROCESSES IN FLAVOPROTEIN-MEDIATED DNA-REPAIR

The flavin photoenzyme, DNA photolyase, utilizes a photon to repair th e main damage to DNA (pyrimidine dimers) caused by UV light. DNA photo lyases are monomeric flavoproteins that bind to the cis-syn-pyrimidine dimer in DNA in a light-independent step, forming a stable enzyme-sub strate complex. This complex absorbs a photon, leading to electron tra nsfer to the pyrimidine dimer, producing an unstable cyclobutane radic al anion and thereby initiating bond cleavage in the dimer. The mechan ism and energetics involved in the action of this remarkable enzyme ar e reviewed.