1. Graduate School of Life and Environmental Sciences Kyoto Prefectural University 1–5 Hangi-cho, Shimogamo Sakyo-ku, Kyoto, Kyoto 606-8522 Japan
2. Current address: Division of Biological Science Nara Institute of Science and Technology Ikoma Nara 630-0192 Japan
3. Medical Research Institute Tokyo Medical and Dental University (TMDU) 1-5-45 Yushima Bunkyo-ku Tokyo 113-8510 Japan
4. Chemistry and Chemical Bioengineering Unit Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna Okinawa 904-0495 Japan
5. Current address: Research Center for Infection Control Omura Satoshi Memorial Institute Kitasato University Shirokane Tokyo 108-8641 Japan
6. Department of Biochemistry Institute for Protein Design and Howard Hughes Medical Institute University of Washington Seattle WA 98195 USA