title: Synthesis and evaluation of TAC-based inhibitors of papain as mimics of cystatin B.
abstract: An approach for mimicking protein-protein interactions by using a discontinuous epitope to construct a mimic that is about one tenth of the size of a natural inhibitor of papain, namely, cystatin B, is described. The discontinuous epitope of cystatin B, which is involved in the interaction with papain, was mimicked by synthesis of a tripodal molecular construct by using the triazacyclophane (TAC) scaffold. The mimic contains three peptide arms: one that mimics the N terminus, one that mimics the C terminus, and one that mimics the beta-hairpin loop structure of cystatin B. These peptide sequences were assembled on the TAC scaffold. The resulting cystatin mimic, CysTACtin 9, showed excellent inhibition of papain with a K(i) of 12 nM, which approaches the inhibitory potency of cystatin B (K(i)=0.12 nM). Experiments with molecular constructs that contained one or two arms or a mixture of the nonscaffolded peptides showed that both scaffolding and the presence of the three peptide arms are crucial for a successful mimic.
authors: Department of Medicinal Chemistry and Chemical Biology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.
authors: Dirk-Jan
authors: DJ
authors: van Zoelen
authors: Maarten R
authors: MR
authors: Egmond
authors: Roland J
authors: RJ
authors: Pieters
authors: Rob M J
authors: RM
authors: Liskamp
mesh_terms: D001372:Aza Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites; D003500:Cyclization; D055313:Cystatin B; D015891:Cystatins / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D000939:Epitopes; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D010206:Papain / Q000037:antagonists & inhibitors* / Q000737:chemistry; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
chemical_list: D001372:Aza Compounds; D015891:Cystatins; D004791:Enzyme Inhibitors; D000939:Epitopes; D055313:Cystatin B; D010206:Papain