1. Departments of Molecular Biology (Y.-K.L., M.C., L.P., S.A.K.), Dallas, Texas 75390
2. Pharmacology (D.R.S., C.L.C., Y.Z., D.J.M., S.A.K.), Dallas, Texas 75390
3. the Howard Hughes Medical Institute (D.R.S., C.L.C., Y.Z., D.J.M.), University of Texas Southwestern Medical Center, Dallas, Texas 75390
4. GlaxoSmithKline Research and Development (B.G.), Research Triangle Park, North Carolina 27709
5. Biochemistry (R.E.H.), Dallas, Texas 75390