1. Department of Biology, Technion–Israel Institute of Technology, Haifa 32000, Israel.
2. Department of Biotechnology and Food Engineering and The Russell Berrie Nanotechnology Institute, Technion–Israel Institute of Technology, Haifa 32000, Israel.
3. Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK.
4. Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany.
5. Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA.