1. Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, and Biochemistry and Cell Biology, Faculty of Veterinary Medicine and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, Netherlands
2. The Cell Microscopy Center, Department of Cell Biology and Institute of Biomembranes, University Medical Center Utrecht, 3584 CX Utrecht, Netherlands
3. Medical Biochemistry, Institute of Biomedicine, University of Helsinki, Helsinki 00014, Finland