1. Center for Integrated Protein Science Munich Technische Universität München Department of Chemistry Lichtenbergstraße 4 85748 Garching Germany
2. Institute of Structural Biology Helmholtz Zentrum München Ingolstädter Landstr. 1 85764 Neuherberg Germany
3. Laboratory of Structural Biophysics Biochemistry and Biophysics Center National Heart, Lung, and Blood Institute National Institutes of Health Building 50 Bethesda MD 20814 USA
4. Institute of Molecular Biology & Biochemistry Center of Molecular Medicine Medical University of Graz 8010 Graz Austria