1. Institut Pasteur; Unité de Chimie des Biomolécules; 28 rue du Dr. Roux 75724 Paris Cedex 15 France
2. CNRS UMR 3523; Institut Pasteur; 75015 Paris France
3. Université Paris Descartes; Institut Pasteur; 75015 Paris France
4. Present address for J.B.: Adisseo (France), Present address for P.B.; Dept. of Organic Chemistry; Arrhenius Laboratory; Stockholm University; 10691 Stockholm Sweden
5. Chemical and Physical Biology; Centro de Investigaciones Biológicas, CSIC; Ramiro de Maeztu 9 28040 Madrid Spain
6. Institut Pasteur; Unité de Pathogénie Microbienne Moléculaire; 28 rue du Dr. Roux 75015 Paris France
7. INSERM U1202; Institut Pasteur; 75015 Paris France
8. Institut Pasteur, PF5; 28 rue du Dr. Roux 75015 Paris France
9. CNRS UMR 3528; Institut Pasteur, 75015; Paris France
10. Molecular Recognition & Host-Pathogen Interactions Program; CIC bioGUNE, Bizkaia Technological Park, Building 801A; 48160 Derio Spain
11. Ikerbasque; Basque Foundation for Science; Maria Lopez de Haro 3 48013 Bilbao Spain