title: Role of calcium in the conformational dynamics of factor XIII activation examined by hydrogen-deuterium exchange coupled with MALDI-TOF MS.
abstract: Factor XIII catalyzes formation of γ-glutamyl-ε-lysyl crosslinks within fibrin clots. FXIII A(2) can be activated proteolytically with thrombin and low mM Ca(2+) or nonproteolytically with high monovalent/divalent cations along with low mM Ca(2+). Physiologically, FXIII A(2) is poised to respond to transient influxes of Ca(2+) in a Na(+) containing environment. A successful strategy to monitor FXIII conformational events is hydrogen-deuterium exchange (HDX) coupled with mass spectrometry. FXIII A(2) was examined in the presence of different cations (Ca(2+), Mg(2+), Ba(2+), Cu(2+), Na(+), TMAC(+), and EDA(2+)) ranging from 1 to 2mM, physiological Ca(2+) concentration, to 50-500mM for nonproteolytic activation. Increases in FXIII solvent exposure could already be observed at 1mM Ca(2+) for the dimer interface, the catalytic site, and glutamine substrate regions. By contrast, solvent protection was observed at the secondary cleavage site. These events occurred even though 1mM Ca(2+) is insufficient for FXIII activation. The metals 1mM Mg(2+), 1mM Ba(2+), and 1mM Cu(2+) each led to conformational changes, many in the same FXIII regions as Ca(2+). FXIII could also be activated nonproteolytically with 500mM tetramethylammonium chloride (TMAC(+)) and 500mM ethylenediamine (EDA(2+)), both with 2mM Ca(2+). These different HDX studies help reveal the first FXIII segments that respond to physiological Ca(2+) levels.
authors.affiliation: Chemistry Department, University of Louisville, 2320 South Brook Street, Louisville, KY 40292, USA.
authors.forename: Ricky T
authors.initials: RT
authors.lastname: Woofter
authors.forename: Muriel C
authors.initials: MC
authors.lastname: Maurer
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D003903:Deuterium / Q000032:analysis; D041961:Deuterium Exchange Measurement; D005176:Factor XIII / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D011503:Transglutaminases / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D006859:Hydrogen; D005176:Factor XIII; D003903:Deuterium; D011503:Transglutaminases; D002118:Calcium