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.