1. Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany.
2. Max-Planck Institute of Biochemistry, Martinsried, Germany.
3. Institute of Virology, Technical University of Munich, School of Medicine, Munich, Germany.
4. German Center for Infection Research (DZIF), Munich, Germany.
5. Physics Department, Technical University of Munich, Garching, Germany.