1. Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom, Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, Department of Biochemistry, Proteomics Centre, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom, and Institute of Comparative Medicine, Faculty of Veterinary Sciences, University of Glasgow, United Kingdom