title: Conformational study of proteins by SAXS and EDXD: the case of trypsin and trypsinogen.
abstract: The radius of gyration (Rg) of bovine trypsinogen and beta-trypsin was measured by an energy-dispersive X-ray technique (EDXD) and by small-angle X-ray scattering (SAXS), under different solvent conditions. Both techniques gave superimposable results. The experimental evidence demonstrated that: (1) no structural modifications and/or damage occurred during the data acquisition by EDXD; (2) at pH 4 the active enzyme has one class of chloride binding sites in common with the zymogen, whereas the latter protease shows an additional class able to reverse the effects on Rg induced by chloride at low concentration; and (3) the pH profile of the Rg of both proteases does not resemble at all the pH effect on beta-trypsin activity, a result in line with the finding that the electrical potentials induced by surface charge are small in absolute magnitude and produce no gradient across the active site.
authors.affiliation: Dipartimento di Fisica, Università di Roma La Sapienza, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Caracciolo
authors.forename: G
authors.initials: G
authors.lastname: Amiconi
authors.forename: L
authors.initials: L
authors.lastname: Bencivenni
authors.forename: G
authors.initials: G
authors.lastname: Boumis
authors.forename: R
authors.initials: R
authors.lastname: Caminiti
authors.forename: E
authors.initials: E
authors.lastname: Finocchiaro
authors.forename: B
authors.initials: B
authors.lastname: Maras
authors.forename: C
authors.initials: C
authors.lastname: Paolinelli
authors.forename: A
authors.initials: A
authors.lastname: Congiu Castellano
mesh_terms: D000818:Animals; D002384:Catalysis; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D011487:Protein Conformation; D012542:Scattering, Radiation; D012965:Sodium Chloride / Q000494:pharmacology; D014357:Trypsin / Q000737:chemistry*; D014362:Trypsinogen / Q000737:chemistry*; D014961:X-Ray Diffraction / Q000379:methods*; D014965:X-Rays
chemical_list: D012965:Sodium Chloride; D014362:Trypsinogen; D014357:Trypsin