Department of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.|Department of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.|Department of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.|Department of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.|Department of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.