1. Section of Structural and Synthetic Biology, Department of Infectious Disease, Imperial College London, London SW7 2AZ, United Kingdom
2. London Consortium for High Resolution cryoEM, the Francis Crick Institute, London NW1 1AT, United Kingdom
3. Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
4. DNA processing machines laboratory, the Francis Crick Institute, London NW1 1AT, United Kingdom