1. Institute for Cell Biology and Immunology, University of Stuttgart Allmandring 31 70569 Stuttgart Germany
2. Institute for General Genetics (240), University of Hohenheim Garbenstrasse 30 70599 Stuttgart Germany
3. Interfaculty Institute for Cell Biology, Proteome Center Tuebingen, University of Tuebingen Auf der Morgenstelle 15 72076 Tuebingen Germany