1. Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
2. Janelia Farm Research Campus HHMI, Ashburn, VA 20147, USA
3. Buchmann Institute for Molecular Life Sciences and Institute of Biochemistry, Goethe University, Max-von-Laue-Strasse 15, 60438 Frankfurt, Germany