title: Structure of a hybrid squash inhibitor in complex with porcine pancreatic elastase at 1.8 A resolution.
abstract: The crystal structure of porcine pancreatic elastase in complex with a hybrid squash inhibitor (HEI-TOE I; 28 amino acids) has been determined to a resolution of 1.8 A. To construct the hybrid inhibitor, the trypsin-binding loop of the squash inhibitor from Ecballium elaterium was substituted by the sequence of a peptide that was derived from the third domain of the turkey ovomucoid inhibitor and was optimized to inhibit porcine pancreatic elastase. This modification of the squash inhibitor changed its specificity for trypsin to a specificity for porcine pancreatic elastase. Specific interactions of this hybrid inhibitor with porcine pancreatic elastase and the differences from the interactions of the ovomucoid inhibitor with human leukocyte elastase are discussed. The binding loop of the inhibitor adopts a 'canonical' conformation and the scissile bond Leu-Glu remains intact.
authors.affiliation: Institut für Biochemie, Universitätsklinikum Charité, Humboldt-Universität zu Berlin, Abteilung Proteinstrukturforschung, Monbijoustrasse 2, 10117 Berlin, Germany.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Aÿ
authors.forename: Kai
authors.initials: K
authors.lastname: Hilpert
authors.forename: Norbert
authors.initials: N
authors.lastname: Krauss
authors.forename: Jens
authors.initials: J
authors.lastname: Schneider-Mergener
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Höhne
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D028464:Cucurbita / Q000737:chemistry; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010196:Pancreatic Elastase / Q000737:chemistry* / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry; D015842:Serine Proteinase Inhibitors / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity; D013552:Swine; D014359:Trypsin Inhibitor, Kazal Pancreatic / Q000737:chemistry
chemical_list: D010446:Peptide Fragments; D015842:Serine Proteinase Inhibitors; C039345:ovomucoid inhibitors; D014359:Trypsin Inhibitor, Kazal Pancreatic; D010196:Pancreatic Elastase