The reaction mixtures (25 μl) contained 25 mM HEPES–NaOH (pH 7.5), 50 mM sodium acetate, 10 mM Mg(CH3COO)2, 1 mM DTT, 0.25 mg/ml BSA, 0.5 mM ATP-γ-S, 0.5 mM CaCl2, 10 fmol of 32P-labeled bubble substrate, and the indicated amount of Mcm4/6/7 proteins.