1. UMR 7175-LC1, CNRS/ULP, ESBS, Parc d'Innovation, Bld S. Brant, BP 10413, 67412 Illkirch Cedex, France, UMR 7104, Structural Biology and Genomics Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP 10142 F-67404 Illkirch Cedex, France, and Laboratory of Cellular and Molecular Immunology, Department of Molecular and Cellular Interactions, Vlaams Interuniversitair Instituut vor Biotechnologie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium