1. Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
2. Center for Integrated Protein Science Munich at the Department Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
3. Molecular Biology of Archaea, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany