AUTOIMMUNE ADDISONS-DISEASE - ANALYSIS OF AUTOANTIBODY BINDING-SITES ON HUMAN STEROID 21-HYDROXYLASE

Human steroid 21 -hydroxylase (21-OH) expressed in an in vitro transla tion system was found to react specifically with adrenal autoantibodie s from patients with Addison's disease. The epitopes on 21-OH which re acted with autoantibodies were studied by incorporating a series of te rminal and internal deletions into the 21-OH gene and analysing the ex pressed proteins by Western blotting. N-Terminal deletions up to amino acid 280 had no effect on autoantibody binding whereas a series of C- terminal deletions and truncations (amino acids 281-494) showed marked effects. Our results indicate that a central segment (281-379) and a C-terminal segment (380-494) of 21-OH interact to form at least one ma jor autoantibody binding site.