1. Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037;
2. Unidad de Biofisica (Centro Mixto CSIC-UPV/EHU), Leioa 48940, Spain;
3. Departamento de Biochimica y Biología Molecular, Universidad del Pais Vasco, Leioa 48940, Spain
4. IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain