1. Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Organic Chemistry for Life Science, Kobe Pharmaceutical University, Higashinada-ku, Kobe, Hyogo 658-8558, Japan, Division of Supramolecular Biology, Institute for Chemical Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710