1. *Institute of Zoology, Department of Molecular Evolution and Genomics, University of Heidelberg, D-69120 Heidelberg, Germany;
2. Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, Basel, Switzerland;
3. Department of Cell Biology and Human Anatomy, University of California at Davis, Davis, CA 95616;
4. School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK