Lucia Banci1, Wolfgang Baumeister2, Udo Heinemann3, Gunter Schneider4, Israel Silman5, David I Stuart7 and Joel L Sussman6 
1Centro Risonanze Magnetiche, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino (Florence) 50019, Italy
2Max Planck Institute of Biochemistry, Am Klopferspitz 18a, Martinsried D-82152, Germany
3Max-Delbrück-Center for Molecular Medicine, Robert-Roessle-Str 10, Berlin D-13125, Germany
4Karolinska Institutet, Scheelevägen 2, Stockholm S-171 77, Sweden
5Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel
6Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
7Division of Structural Biology, Oxford University, Oxford OX3 7BN, UK