1. Department of Biochemistry III, University of Regensburg, Universitätstrasse 31, 93053 Regensburg, Germany
2. Department of Molecular Biology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
3. Göttingen Center for Molecular Biosciences, Georg-August University, Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany