Effect of 11 selected TF mutations on the ability of Mg2+ to enhance the rate of FX activation by TF/FVIIa/membrane complexes. WT or mutant memTF was incorporated into liposomes containing 0-15% PS, with the balance being PC. Initial rates of FX activation by the resulting memTF/FVIIa complexes were measured with 1.25 mM Ca2+ and 0.6 mM Mg2+ and normalized to the rates observed with 1.85 mM Ca2+ alone. The memTF mutants are grouped in the three panels as described in the text, with the same data for WT memTF (●) plotted in each panel for comparison. (A) Normalized rates of FX activation observed with memTF mutants S162A (⨯), W158A (▼), E174A (∇), and D178A (✯). (B) Normalized rates of FX activation observed with memTF mutants S163A (□), K165A (◆), K159A (○), and Y157A (▲). (C) Normalized rates of FX activation observed with memTF mutants Y185A (∆), K166A (■), and G164A (◊). Data are means ± the standard error (n ≥ 3).