1. Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia Vancouver British Columbia Canada V6T 1Z3
2. Department of Membrane Biochemistry and Biophysics, Bijvoet Center and Institute of Biomembranes, Utrecht University 3584 CH Utrecht The Netherlands
3. Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health Bethesda Maryland 20892 USA