How an enzyme uses sunlight for DNA repair
Structure of the photolyase with bound DNA (yellow and blue) and the photochemically active area (purple).
An international team of researchers led by the German Electron Synchrotron (DESY) and the University of Hamburg, which included Ajda Kunavar (D13) a researcher from the National Institute of Chemistry, has shown how the enzyme photolyase efficiently channels the energy of sunlight into DNA repair. The results have been published in Science (IF: 56.9).
Living organisms have to cope with harmful UV rays that can cause DNA damage. UV rays can cause DNA cross-linking, which can cause defects in the genetic code, and also lead to cell death or - in the worst case - mutagenesis and cancer. To survive, organisms have therefore developed various DNA repair mechanisms, including photolyase. This enzyme uses sunlight to repair the damage caused by it. Photolyase is able to identify specific sites on the DNA where UV radiation has cross-linked it. Upon attaching to these sites, it can absorb blue photons and use them to perform repair chemistry, turning the DNA back into its original, healthy form.
In recent decades, researchers have studied whether the two carbon-carbon bonds involved in the repair process broke simultaneously, or in a stepwise fashion. Using time-resolved crystallography, the researchers have now confirmed the stepwise mechanism. The study also showed that the enzyme has a binding site that perfectly matches the shape of the damaged DNA. The repaired DNA does not fit into this pocket, as it is too large and has the wrong shape. This explains why photolyase has a higher affinity for the damaged DNA than for the repaired, healthy DNA.
More: https://www.science.org/doi/10.1126/science.adj4270
Info: ajda.kunavar(at)ki.si