1. Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829, Japan
2. Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
3. Innovative Drug Research Laboratories, Kyowa Hakko Kirin Co. Ltd., Machida, Tokyo 194-8533, Japan
4. Chemical Genetics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan