1. Department of Clinical Biochemistry, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 2QR, U.K.
2. Division of Endocrinology, Department of Medicine, SUNY at Stony Brook, Stony Brook, NY 11794-8154, U.S.A.
3. Department of Molecular Biology, Max-Planck Institut fur Biochemie, 8033 Martinsried, Federal Republic of Germany.