Comparison of two different benzodiazepine binding proteins by peptide mapping after limited proteolysis

Proteins P₅₁ and P₅₅ were photolabeled by [³H]flunitrazepam, [³H]clonazepam or ³H-Ro 15–4513 and then compared by peptide mapping after limited digestion with various proteases. Results indicated that [³H]flunitrazepam or [³H]clonazepam irreversibly bind to the same and [³H]Ro 15–4513 to a different part of these proteins. The different radiolabeled peptide patterns obtained from P₅₁ or P₅₅ irrespective of the photolabel used, suggest a difference in the molecular structure of these proteins.