1. Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan
2. Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
3. Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.