title: Hydrogen exchange kinetics of bovine pancreatic trypsin inhibitor beta-sheet protons in trypsin-bovine pancreatic trypsin inhibitor, trypsinogen-bovine pancreatic trypsin inhibitor, and trypsinogen-isoleucylvaline-bovine pancreatic trypsin inhibitor.
abstract: Hydrogen exchange rates of six beta-sheet peptide amide protons in bovine pancreatic trypsin inhibitor (BPTI) have been measured in free BPTI and in the complexes trypsinogen-BPTI, trypsinogen-Ile-Val-BPTI, bovine trypsin-BPTI, and porcine trypsin-BPTI. Exchange rates in the complexes are slower for Ile-18, Arg-20, Gln-31, Phe-33, Tyr-35, and Phe-45 NH, but the magnitude of the effect is highly variable. The ratio of the exchange rate constant in free BPTI to the exchange rate constant in the complex, k/kcpIx, ranges from 3 to much greater than 10(3). Gln-31, Phe-45, and Phe-33 NH exchange rate constants are the same in each of the complexes. For Ile-18 and Tyr-35, k/kcpIx is much greater than 10(3) for the trypsin complexes but is in the range 14-43 for the trypsinogen complexes. Only the Arg-20 NH exchange rate shows significant differences between trypsinogen-BPTI and trypsinogen-Ile-Val-BPTI and between porcine and bovine trypsin-BPTI.
mesh_terms: D000818:Animals; D007611:Aprotinin / Q000378:metabolism*; D002417:Cattle; D004151:Dipeptides / Q000378:metabolism*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D013552:Swine; D014357:Trypsin / Q000378:metabolism*; D014362:Trypsinogen / Q000378:metabolism*
chemical_list: D004151:Dipeptides; C041115:isoleucylvaline; D014362:Trypsinogen; D007611:Aprotinin; D014357:Trypsin