title: The effect of divalent metal ions on the electrophoretic mobility of bovine prothrombin and bovine prothrombin fragment 1.
abstract: Examination of metal ion-dependent effects on the electrophoretic mobility of bovine prothrombin and fragment 1 provides a useful and sensitive method for investigation of conformational processes in these proteins. Utilization of this method reveals a conformational change in bovine prothrombin and fragment 1 which occurs at low metal ion concentrations. Equilibrium dialysis studies indicate that the metal ion-induced shape change occurs concomitant with binding of a single calcium ion/molecule of prothrombin or fragment 1. Mixed metal electrophoretic mobility studies with Mg2+ and Ca2+ have demonstrated the "synergistic" effect for fragment 1 observed by others. Mixed metal equilibrium dialysis has provided experimental support for this observation and allows us to conclude that two tight Ca2+ sites are not affected by low Mg2+ concentrations and that the third Ca2+ site is also a tight site for Mg2+. Thus, at low Mg2+ concentrations and upon the addition of Ca2+, there are effectively three tight sites; consequently more Ca2+ will bind to the protein at lower total Ca2+ ion concentrations.
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002413:Cations, Divalent; D002417:Cattle; D004357:Drug Synergism; D004591:Electrophoresis, Polyacrylamide Gel; D008274:Magnesium / Q000494:pharmacology*; D010446:Peptide Fragments / Q000378:metabolism; D011487:Protein Conformation / Q000187:drug effects; D011498:Protein Precursors; D011516:Prothrombin / Q000378:metabolism; D013324:Strontium / Q000494:pharmacology*
chemical_list: D002413:Cations, Divalent; D010446:Peptide Fragments; D011498:Protein Precursors; C029733:prothrombin fragment 1; D011516:Prothrombin; D008274:Magnesium; D002118:Calcium; D013324:Strontium