Is Ca(II) ion binding to prothrombin fragment 1 intrinsically cooperative, or is the cooperative binding accounted for by self-association?
The recent suggestion that the apparent cooperativity seen in the binding of Ca(II) ions to prothrombin fragment 1 is due to protein aggregation is evaluated. Since (1) we find that the Ca(II) ion binding is not dependent upon protein concentration, (2) the analytical expression for the equilibrium constant of the aggregation model is unrealistically large when evaluated at realistic Ca(II) ion concentrations, and (3) a very simple allosteric cooperative binding model (Monod) can be shown to fit the experimental data, we conclude that the aggregation explanation for the apparent cooperativity in the Ca(II) ion binding by prothrombin fragment 1 is not correct.
Cabaniss
S
S
Department of Chemistry, Kent State University, OH 44242, USA.
Deerfield
D W
DW
Monroe
D M
DM
Hiskey
R G
RG
Pedersen
L G
LG
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent; D002417:Cattle; D003956:Dialysis; D046911:Macromolecular Substances; D008433:Mathematics; D008956:Models, Chemical; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism*; D011516:Prothrombin / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics
D002413:Cations, Divalent; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011498:Protein Precursors; C029733:prothrombin fragment 1; D011516:Prothrombin; D002118:Calcium