1. Department of Chemistry, Michigan State University, East Lansing, MI 48824.
2. Max-Planck-Institut für Biochemie, D-8033 Martinsried, Federal Republic of Germany.
3. Transgene S.A., 67082 Strasbourg Cedex, France.
4. Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany, NY 12201, and Departrnents of Physiology and Biochemistry, The Albany Medical College of Union University, Albany, NY 12208.