1. Faculty of Biology, Ludwig-Maximilian-Universität München, 82152 Planegg-Martinsried, Germany.
2. Graduate School Life Science Munich, Planegg, Germany.
3. Zellbiologie, Universität Bayreuth, 95440 Bayreuth, Germany.
4. Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA.
5. Department of Physiology, University of California, San Francisco, San Francisco, CA 94143, USA.