1. Division of Structural Biology Wellcome Centre for Human Genetics Roosevelt Drive Oxford OX3 7BN UK
2. The Research Complex at Harwell Harwell Campus Oxford OX11 0FA UK
3. The Rosalind Franklin Institute Harwell Campus Oxford OX11 0FA UK
4. Department of Chemistry Frick Chemistry Laboratory Princeton University Princeton NJ USA
5. Biomedical Sciences Research Complex, North Haugh University of St. Andrews Fife KY16 9ST UK
6. Department of Biology Institute of Microbiology Eidgenössische Technische Hochschule (ETH) Zürich Zürich Switzerland