1. Department of Life Sciences, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
2. MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK.
3. National Heart and Lung Institute, Imperial College, London, UK.
4. Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
5. Private University in the Principality of Liechtenstein, Triesen, Liechtenstein.