title: High-resolution structures of a chitinase complexed with natural product cyclopentapeptide inhibitors: mimicry of carbohydrate substrate.
abstract: Over the past years, family 18 chitinases have been validated as potential targets for the design of drugs against human pathogens that contain or interact with chitin during their normal life cycles. Thus far, only one potent chitinase inhibitor has been described in detail, the pseudotrisaccharide allosamidin. Recently, however, two potent natural-product cyclopentapeptide chitinase inhibitors, argifin and argadin, were reported. Here, we describe high-resolution crystal structures that reveal the details of the interactions of these cyclopeptides with a family 18 chitinase. The structures are examples of complexes of a carbohydrate-processing enzyme with high-affinity peptide-based inhibitors and show in detail how the peptide backbone and side chains mimic the interactions of the enzyme with chitooligosaccharides. Together with enzymological characterization, the structures explain why argadin shows an order of magnitude stronger inhibition than allosamidin, whereas argifin shows weaker inhibition. The peptides bind to the chitinase in remarkably different ways, which may explain the differences in inhibition constants. The two complexes provide a basis for structure-based design of potent chitinase inhibitors, accessible by standard peptide chemistry.
authors.affiliation: Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Houston
authors.forename: Kazuro
authors.initials: K
authors.lastname: Shiomi
authors.forename: Noriko
authors.initials: N
authors.lastname: Arai
authors.forename: Satoshi
authors.initials: S
authors.lastname: Omura
authors.forename: Martin G
authors.initials: MG
authors.lastname: Peter
authors.forename: Andreas
authors.initials: A
authors.lastname: Turberg
authors.forename: Bjørnar
authors.initials: B
authors.lastname: Synstad
authors.forename: Vincent G H
authors.initials: VG
authors.lastname: Eijsink
authors.forename: Daan M F
authors.initials: DM
authors.lastname: van Aalten
mesh_terms: D000818:Animals; D002241:Carbohydrates; D002688:Chitinases / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D046911:Macromolecular Substances; D008958:Models, Molecular; D018716:Molecular Mimicry; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry* / Q000494:pharmacology*; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000494:pharmacology*; D013379:Substrate Specificity
chemical_list: D002241:Carbohydrates; D004791:Enzyme Inhibitors; D046911:Macromolecular Substances; D009842:Oligopeptides; D010456:Peptides, Cyclic; D002688:Chitinases