Mlh1-Mlh3 binding to DNA displays a sigmoidal pattern.

<p>(A) Nitrocellulose filter binding reactions for linearized 2.7 kb, 7 kb, or 12 kb DNA. The fraction of nitrocellulose-bound DNA was plotted as a function of Mlh1-Mlh3 concentration on a log-scale. For the 2.7-kb substrate, data are for four independent experiments. For the 7 kb and 12 kb substrates, three replicates were performed. All reactions were carried out for 10 min. The average is plotted with error bars representing the standard deviation between experiments. (B) Nitrocellulose filter binding reaction. Increasing amounts of Mlh1-Mlh3 were incubated with 7 kb linear DNA in a buffer containing either 20 mM KCl or 150 mM KCl (all buffers contained 2 mM Mg²⁺). The reaction was performed in triplicate. The average and standard deviation (error bars) are shown here. (C) Nicking reaction. 7 kb linear DNA incubated with increasing amounts yeast Mlh1-Mlh3 in a buffer containing either 20 mM KCl or 150 mM KCl. Endonuclease conditions are identical to those previously published, with a reaction time of 60 min [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2001164#pbio.2001164.ref026" target="_blank">26</a>]. Activity was assayed for two independent experiments and quantified by alkaline agarose gel electrophoresis.