1. Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712-1167, Department of Integrative Biology and Pharmacology, University of Texas Medical School, 6431 Fannin Street, Houston, Texas 77030, Howard Hughes Medical Institute, Department of Biochemistry, and the Department of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9041, and Department of Physiology and Biophysics, State University of...