1. Department of Cell Biology and Institute of Biomembranes, University Medical Center Utrecht, 3584 CX, Utrecht, The Netherlands
2. Protein Metabolism Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan
3. BioScience Center, San Diego State University, San Diego, CA 92182, USA
4. Department of Biochemistry, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway