Our DNA is every day subjected to external and internal damaging agents and understanding the mechanisms of DNA repair at a molecular level is increasingly important in order to address future challenges for the human health. This project aims to reveal n ew information about molecular mechanisms of Base Excision Repair (BER) by analysing interactions and determining crystal structures of protein complexes from this pathway. Targets will be selected from the genomes of the extremophiles Deinococcus radiodu rans and Vibrio salmonicida. Recombinant proteins will be produced in quantities necessary for interaction studies and protein crystallisation experiments, which will be performed for single proteins and protein complexes using high throughput crystallisa tion technology. Protein complexes will be identified using in vitro pull-down assays and cross-linking experiments, and characterised using Surface Plasmon Resonance (SPR) and Isothermal Titration Calorimetry (ITC) prior to crystallisation experiments, s tructure determination and small angel X-ray scattering (SAXS) experiments. The project will be performed within the infrastructure offered by the Norwegian Structural Biology centre (NorStruct) at the University of Tromsø, and in collaboration with the staff at the centre, the Molecular biology research group (Professor Hans E. Krokan) at the Department of cancer research and molecular medicine at the Norwegian University of Science and Technology (NTNU) and their collaborator (Professor John A. Tainer ) at the Advanced Light Source (ALS) synchrotron beamline at Berkley Lab. (SIBYLS) and the Macromolecular crystallography (MX) group (Dr. Sean McSweeney) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.