Model for TthMutS suppression of mismatched primer-dependent amplification. (A) Schematic representation of the model. Mishybridization of primers at the annealing step generates mismatched bases that are tightly bound by MutS, which block the approach of DNA polymerases to the 3′ end of the primers; (B) The 80-bp perfectly matched template was amplified by AmpliTaq Gold DNA polymerase by real-time PCR using mismatched primers. The threshold cycle (Ct) was determined and plotted against the distance between the mismatched bases and 3′ end of the primer (8, 11, 14, 17, 20 or 23 bp). PM, perfectly matched primer. Blue and gray bars indicate experiments with or without 1.0 μM TthMutS, respectively. Experiments were repeated three times. Bars indicate standard deviations.