title: Conformational studies of human plasminogen and plasminogen fragments: evidence for a novel third conformation of plasminogen.
abstract: The conformations of Glu-plasminogen and defined proteolytic fragments, in the presence and absence of 6-aminohexanoic acid (6-AHA), trans-4-(aminomethyl)cyclohexanecarboxylic acid (t-AMCHA), and benzamidine, were studied using three methods: size-exclusion high-performance liquid chromatography (SE-HPLC), small-angle X-ray scattering (SAXS), and dynamic laser light scattering (DLLS). The well-documented conformational change of Glu-plasminogen with 6-AHA or t-AMCHA was measured as a decrease in molecular elution time by SE-HPLC (8.93 +/- 0.01 to 8.32 +/- 0.01 min) and increases in radius of gyration (30.7 +/- 0.1 to 49.8 +/- 0.3 A) and Stokes radius (40.6 +/- 0.3 to 48.5 +/- 0.3 A) by SAXS and DLLS, respectively. The addition of benzamidine to Glu-plasminogen resulted in a conformation (radius of gyration 41.0 +/- 0.4 A and Stokes radius 46.6 +/- 0.3 A) distinct from that in the presence of 6-AHA. 6-AHA, but not benzamidine, induced significant conformational changes in Lys-plasminogen and kringles 1 + 2 + 3 + 4 + 5. We conclude that Glu-plasminogen adopts three distinct conformations involving two intramolecular interactions: one mediated by regions of the NH2-terminal peptide and kringle 5, competed for by 6-AHA or benzamidine, and the other possibly between kringles 3 and 4, competed for by 6-AHA but not benzamidine.
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Headington, U.K.
authors.forename: J M
authors.initials: JM
authors.lastname: Marshall
authors.forename: A J
authors.initials: AJ
authors.lastname: Brown
authors.forename: C P
authors.initials: CP
authors.lastname: Ponting
mesh_terms: D015119:Aminocaproic Acid / Q000494:pharmacology; D001550:Benzamidines / Q000494:pharmacology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008027:Light; D010446:Peptide Fragments / Q000737:chemistry*; D010958:Plasminogen / Q000737:chemistry*; D011487:Protein Conformation; D012542:Scattering, Radiation; D014148:Tranexamic Acid / Q000494:pharmacology; D014965:X-Rays
chemical_list: D001550:Benzamidines; D010446:Peptide Fragments; D014148:Tranexamic Acid; D010958:Plasminogen; C032157:benzamidine; D015119:Aminocaproic Acid