1. Department of Biological Functions and Engineering, Kyushu Institute of Technology, Kitakyushu Science and Research Park, 2-4 Hibikino, Wakamatsu-ku, Fukuoka 808-0196, Japan, Department of Biological Information, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan, and Department of Biosciences, Division of Biochemistry, Viikki Biocenter, 00014, University of Helsinki, P.O. Box 56, Helsinki, Finland