Division of Structural Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 07, Sendai 980-8579, Japan; Structural Biology Center, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan; Department of Pathology and Immunology, Washington University School of Medicine, Box 8118, 660 South Euclid Avenue, St....(At 2003-07-09)