The Norwegian Structural Biology Center and the Center for Theoretical Computational Chemistry, Department of Chemistry, Faculty of Science and Technology, University of Tromsø, Tromsø, Norway.|Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Uppsala, Sweden.|The Norwegian Structural Biology Center and the Center for Theoretical Computational Chemistry, Department of Chemistry, Faculty of Science and Technology, University of Tromsø, Tromsø, Norway.