1. Molecular Membrane Biology Laboratory, RIKEN, Wako, Saitama 351-0198,1
2. Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602,2
3. Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-0032, 3 and
4. Department of Molecular Biology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, 4 Japan