Howard Hughes Medical Institute, Children's Hospital, Boston, Massachusetts (D.E.C.); Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland C.M.); Pharmakologisches Institut, Freie Universitaet Berlin, Berlin, Germany (G.S.); and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California (D.J.)

Howard Hughes Medical Institute, Children's Hospital, Boston, Massachusetts (D.E.C.); Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland C.M.); Pharmakologisches Institut, Freie Universitaet Berlin, Berlin, Germany (G.S.); and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California (D.J.)

Howard Hughes Medical Institute, Children's Hospital, Boston, Massachusetts (D.E.C.); Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland C.M.); Pharmakologisches Institut, Freie Universitaet Berlin, Berlin, Germany (G.S.); and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California (D.J.)

Howard Hughes Medical Institute, Children's Hospital, Boston, Massachusetts (D.E.C.); Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland C.M.); Pharmakologisches Institut, Freie Universitaet Berlin, Berlin, Germany (G.S.); and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California (D.J.)