Biochemical analysis of Myc and Max. (A) SDS-PAGE of the indicated recombinant proteins that were expressed in E. coli and purified as described in Methods. (B) EMSA using native polyacrylamide gel electrophoresis with 200 ng of the indicated proteins (250 nM Max dimer and 125 nM Myc-Max) with 0, 0.1, 0.3, 1, or 3-fold molar excess of the indicated dsDNA. The gels were silver stained to show the mobility of the proteins. The arrows indicate protein-DNA complexes. (C) EMSA with simultaneous staining of MaxL and Myc-MaxL. A total of 2.5 pmole of each protein (125 nM) per lane with two levels of the indicated DNA probes. Complexes containing indicated proteins are indicated with arrows. Note that in the Myc-Max prep some dissociation of Max has occurred leading to a low level of Max and Max-DNA species. (D, E, F, G, and H) EMSAs using 0.01 nM of the indicated radiolabeled probe (blue) with the indicated concentration of proteins and competitor DNAs.