MBP-MutS-H6 binding reactions contained $11.5 ng/ml DNA and $950 nM MBP-MutS-H6 dimers in 1· binding buffer (20 mM Tris-HCl, pH 7.8, 10 mM NaCl, 5 mM MgCl 2 , 1 mM DTT and 5% glycerol). Reactions were allowed to incubate at room temperature for 10 min before incubation for 30 min with an equal volume of amylose resin pre-equilibrated in 1· binding buffer. Protein-DNA complexes were removed by low-speed centrifugation and aliquots of supernatant were removed for subsequent processing.