title: The three-dimensional structure of the bifunctional proteinase K/alpha-amylase inhibitor from wheat (PK13) at 2.5 A resolution.
abstract: Wheat germ contains an inhibitor for proteinase K, called PK13 (Mr approximately 19,600) which simultaneously inhibits alpha-amylase. PK13 was crystallized, space group P21, a = 43.02 (5) A, b = 65.18 (7) A, c = 32.33 (4) A, beta = 112.79 degrees (9), X-ray data were collected to 2.5 A resolution, the structure solved by molecular replacement on the basis of the atomic coordinates of the homologous Erythrina caffra DE-3 inhibitor, and refined with simulated annealing techniques with a current R-factor of 21%. The three-dimensional structure of PK13 is stabilised by two disulfide bridges and has a central beta-barrel with distorted beta-structure. In analogy to related inhibitors, the binding site for proteinase K is assumed to be located on the surface of the protein (amino acid residues 66-67), although the 75-76 peptide bond is cleaved upon binding.
authors.affiliation: Institut für Kristallographie, Freie Universität Berlin, Germany.
authors.forename: K J
authors.initials: KJ
authors.lastname: Zemke
authors.forename: A
authors.initials: A
authors.lastname: Müller-Fahrnow
authors.forename: K D
authors.initials: KD
authors.lastname: Jany
authors.forename: G P
authors.initials: GP
authors.lastname: Pal
authors.forename: W
authors.initials: W
authors.lastname: Saenger
mesh_terms: D001665:Binding Sites; D019286:Endopeptidase K; D004791:Enzyme Inhibitors; D010940:Plant Proteins / Q000648:ultrastructure*; D011487:Protein Conformation; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors; D014908:Triticum / Q000032:analysis*; D000516:alpha-Amylases / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D010940:Plant Proteins; D015842:Serine Proteinase Inhibitors; D000516:alpha-Amylases; D012697:Serine Endopeptidases; D019286:Endopeptidase K