1. Department of Physiology, Tokyo Women's Medical College, Tokyo 162, Japan.
2. Department of Biochemistry, Jichi Medical School, Tochigi-ken 329-04, Japan.
3. Division of Regulation of Macromolecular Function, Institute for Protein Research, Osaka University, Suita 565, Japan.
4. Department of Molecular Neurobiology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108, Japan.