1. Laboratoire d'Enzymologie et Biochimie Structurales (LEBS), CNRS, Bat. 34 1 avenue de la Terrasse 91198 Gif‐sur‐Yvette France
2. European Molecular Biology Laboratory (EMBL), Grenoble Outstation 6 rue Jules Horowitz, BP 181 38042 Grenoble France
3. Section for Electron Microscopy, Leiden University Medical Center (LUMC) 2333 ZC Einthovenweg 20 Leiden The Netherlands