title: The role of gamma-carboxyglutamyl residues in the positive cooperative binding of Ca2+ to blood coagulation factor X.
abstract: 1. The calcium binding properties of factor X and its analogous decarboxyprotein have been compared with the aid of flow rate dialysis and ultraviolet difference spectroscopy. 2. Factor X binds approx. 20 mol of calcium per mol of protein. The first four sites exhibit positive cooperativity. 3. Changes in the ultraviolet difference spectrum when Ca2+ is bound suggest a conformational change. 4. In decarboxyfactor X low affinity of Ca2+ and no ligand-induced conformational change was observed. It is concluded that the presence of gamma-carboxyglutamate residues is a prerequisite for positive cooperative Ca2+ binding.
mesh_terms: D000818:Animals; D002118:Calcium; D002417:Cattle; D005170:Factor X / Q000378:metabolism; D005971:Glutamates; D007700:Kinetics; D011485:Protein Binding
chemical_list: D005971:Glutamates; D005170:Factor X; D002118:Calcium