title: Identification of chymotrypsin inhibitors from a second-generation template assisted combinatorial peptide library.
abstract: In an earlier study (McBride JD, Freeman N, Domingo GJ, Leatherbarrow RJ. Selection of chymotrypsin inhibitors from a conformationally-constrained combinatorial peptide library. J. Mol. Biol. 1996; 259: 819-827) we described a resin-bound cyclic peptide library, constructed based on the sequence of the anti-tryptic reactive site loop of Bowman Birk Inhibitor (BBI), a proteinase inhibitor protein. This library was used to identify re-directed chymotrypsin inhibitors with Ki values as low as 17 nM. We have now extended this work by constructing an enhanced library in which a further position, at the P4 site of the inhibitor, has been randomized. This new library has variation at three target locations (P4, P1 and P2) within the inhibitory loop region, producing 8,000 variants. Screening this library allowed selection of new inhibitor sequences with Ki values as low as 3.4 nM. The success of this approach is reflected by the fact that the inhibition constant given by the selected peptide sequence is slightly lower than that reported against chymotrypsin for the most studied full length BBI protein, Soybean BBI 2-IV.
authors.affiliation: Department of Chemistry, Imperial College of Science, Technology, and Medicine, South Kensington, London, UK.
authors.forename: J D
authors.initials: JD
authors.lastname: McBride
authors.forename: H N
authors.initials: HN
authors.lastname: Freeman
authors.forename: R J
authors.initials: RJ
authors.lastname: Leatherbarrow
mesh_terms: D000595:Amino Acid Sequence; D001710:Biotin / Q000737:chemistry; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D020650:Combinatorial Chemistry Techniques / Q000379:methods*; D016384:Consensus Sequence; D004791:Enzyme Inhibitors / Q000032:analysis*; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019151:Peptide Library; D010456:Peptides, Cyclic / Q000032:analysis; D011480:Protease Inhibitors / Q000032:analysis; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D014358:Trypsin Inhibitor, Bowman-Birk Soybean / Q000032:analysis
chemical_list: D004791:Enzyme Inhibitors; D019151:Peptide Library; D010456:Peptides, Cyclic; D011480:Protease Inhibitors; D014358:Trypsin Inhibitor, Bowman-Birk Soybean; D001710:Biotin; D002918:Chymotrypsin