An equilibrium study of metal ion binding to human plasma coagulation factor XIII.
1. The binding of Ca2+ to plasma coagulation Factor XIII from man and from cow caused a small decrease in the intrinsic fluorescence of the protein with a dissociation constant of 0.1 mM. A similar decrease was observed with the thrombin-activated Factors (Factors XIIa). The decrease in protein fluorescence was also caused by both Ni2+ and Mn2+ but not by Mg2+. 2. 45Ca2+ binding was directly demonstrated by equilibrium dialysis. Ca2+ at 0.2 mM bound to Factor XIII (a2b2) and Factor XIIIa (a'2b2) but not to isolated b2-protein. A tight-binding site for Ca2+ is associated with the a-subunits. 3. The Ca2+ essential for the enzyme activity of Factor XIII from man, pig and cow can be replaced by Ni2+, Cu2+, La3+, Mn2+, Fe3+, Y3+, Co2+, Sr2+ or Tb3+, but not by Mg2+.
D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002413:Cations, Divalent / Q000378:metabolism*; D002417:Cattle; D003956:Dialysis; D005176:Factor XIII / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D013050:Spectrometry, Fluorescence; D013917:Thrombin
D002413:Cations, Divalent; D005176:Factor XIII; D013917:Thrombin; D002118:Calcium