1. Department of Biochemistry and NMR Laboratory, Kobe Pharmaceutical University, Higashinada-ku, Kobe 658-8558, Japan, Department of Biological Sciences, Imperial College, London SW7 2AZ, United Kingdom, and Institute of Biological Chemistry, Academia Sinica, 128, Academia Road Sec 2, Nankang, Taipei 115, Taiwan, R.O.C.