1. Institute of Microbiology, Eidgenössische Technische Hochschule Wolfgang‐Pauli Strasse 10 Zurich 8093 Switzerland
2. Department of Cellular Machines, Centre for Biotechnology, University of Technology Tatzberg 47 Dresden 01307 Germany
3. Department of Structural Biology, Max Planck Institute of Biophysics Max‐von‐Laue Strasse 3, Frankfurt am Main 60438 Germany