1. *Signalling and Motility Group,
2. Institute of Biophysical Chemistry, Hannover Medical School, D-30623 Hannover, Germany; and
3. Institute of Molecular Biotechnology, Austrian Academy of Sciences, A-1030 Vienna, Austria
4. Department of Cell Biology, German Research Centre for Biotechnology, D-38124 Braunschweig, Germany;
5. Cytoskeleton Dynamics Group, and