1. College of Pharmacy and Center for Gene Research and Biotechnology, Oregon State University, Corvallis, Oregon 97331, Vollum Institute for Advanced Biomedical Research and Department of Cell Biology and Anatomy, Oregon Health Sciences University, Portland, Oregon 97201, and Laboratoire Protéines et Récepteurs Membranaires, Ecole Supérieure de Biotechnologie de Strasbourg, F-67400 Illkirch, France