1. Institute for Bioengineering of Catalonia (IBEC), Carrer Baldiri Reixac 15-21, 08024 Barcelona, Spain
2. Electron Cryomicroscopy Unit, Centres Científics i Tecnològics de la Universitat de Barcelona (CCiTUB), Carrer Baldiri i Reixac 10-12, 08028 Barcelona, Spain
3. Department of Biomedical Engineering, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, 5612 AZ Eindhoven, The Netherlands
4. Department of Biological Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Carrer Jordi Girona 18-26, 08034 Barcelona, Spain