1. Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, Leeds LS2 9JT, UK
2. Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB, CSIC), Campus Univ. Autonoma, 3 Darwin Street, Cantoblanco, 28049 Madrid, Spain
3. Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
4. Health Protection Agency, London NW9 5HT, UK