title: Molecular structure of an aspartic proteinase zymogen, porcine pepsinogen, at 1.8 A resolution.
abstract: The only well-understood mechanism of zymogen activation is that of the serine proteinases, in which proteolytic cleavage leads to conformational changes resulting in a functional active site. A different mechanism is now unveiled by the crystal structure of pepsinogen. Salt bridges that stabilize the positioning of the N-terminal proenzyme segment across the active site of pepsin are disrupted at low pH, releasing the amino-terminal segment and thereby exposing the catalytic apparatus and the substrate-binding sites.
mesh_terms: D000818:Animals; D001665:Binding Sites; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D010435:Pepsinogens; D011487:Protein Conformation; D011498:Protein Precursors; D013329:Structure-Activity Relationship; D013552:Swine
chemical_list: D010435:Pepsinogens; D011498:Protein Precursors