1. Structural Biology Unit, CICbioGUNE, Bizkaia Technology Park, Bld.800, 48160, Derio, Spain
2. IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
3. Division of Structural Biology and the Oxford Protein Production Facility, The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Headington, Oxford, OX3 7BN, UK
4. Institute of Biotechnology and Department of Biological and Environmental Sciences, Viikki Biocenter, University of Helsinki P.O. Box 56, Viikinkaari 5, 00014, University of Helsinki, Finland