title: Three-dimensional structure of the complexes between bovine chymotrypsinogen A and two recombinant variants of human pancreatic secretory trypsin inhibitor (Kazal-type).
abstract: Variants of the human pancreatic secretory trypsin inhibitor (PSTI) have been created during a protein design project to generate a high-affinity inhibitor with respect to some serine proteases other than trypsin. Two modified versions of human PSTI with high affinity for chymotrypsin were crystallized as a complex with chymotrypsinogen. Both crystallize isomorphously in space group P4(1)2(1)2 with lattice constants a = 84.4 A, c = 86.7 A and diffract to 2.3 A resolution. The structure was solved by molecular replacement. The final R-value after refinement with 8.0 to 2.3 A resolution data was 19.5% for both complexes after inclusion of about 50 bound water molecules. The overall three-dimensional structure of PSTI is similar to the structure of porcine PSTI in the trypsinogen complex (1TGS). Small differences in the relative orientation of the binding loop and the core of the inhibitors indicate flexible adaptation to the proteases. The chymotrypsinogen part of the complex is similar to chymotrypsin. After refolding induced by binding of the inhibitor the root-mean-square difference of the active site residues A186 to A195 and A217 to A222 compared to chymotrypsin was 0.26 A.
authors.affiliation: GBF (Gesellschaft für Biotechnologische Forschung), Department of Molecular Structure Research, Braunschweig, Germany.
authors.forename: H J
authors.initials: HJ
authors.lastname: Hecht
authors.forename: M
authors.initials: M
authors.lastname: Szardenings
authors.forename: J
authors.initials: J
authors.lastname: Collins
authors.forename: D
authors.initials: D
authors.lastname: Schomburg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002919:Chymotrypsinogen / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D013552:Swine; D014359:Trypsin Inhibitor, Kazal Pancreatic / Q000737:chemistry / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D014359:Trypsin Inhibitor, Kazal Pancreatic; D002919:Chymotrypsinogen