1. Department of Chemistry Graduate School of Science Osaka University 1-1 Machikaneyama Toyonaka, Osaka 560-0043 Japan
2. Forefront Research Center Osaka University 1-1 Machikaneyama Toyonaka Osaka 560-0043 Japan
3. Department of Molecular Biochemistry and Clinical Investigation Graduate School of Medicine Osaka University 1-7 Yamadaoka Suita Osaka 565-0871 Japan
4. Institute of Protein Research Osaka University 3-2, Yamadaoka Suita Osaka 565-0871 Japan
5. Department of Chemistry Massachusetts Institute of Technology B18, R596 77 Massachusetts Ave. Cambridge MA 02139 USA