1. Membrane
Protein Structure Function Unit, National Institute of Neurological
Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
2. Laboratory
of Molecular Biology, National Institute of Diabetes and Digestive
and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, United States
3. Department
of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, United States
4. Departments
of Pharmacology and Biological Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States