Fig. 5. The mutant CeTwist (E29K) protein binds to DNA as a homodimer and as a heterodimer with CeE/DA, whereas the human Saethre-Chotzen mutations in CeTwist bind DNA only as heterodimers with CeE/DA. In vitro gel shift assays were performed using primers containing an E box bHLH binding site. Bacterially expressed and purified proteins added to the assay are indicated across the top of the gel. DA, CeE/DA; Tw, CeTwist; B, CeTwist without the basic DNA-binding domain; E29K, CeTwist with the n2170sd point mutation causing the E29K amino acid change; hQ119P, hR118H and hR116W, CeTwist with the human Saethre-Chotzen amino acid substitutions. Protein/DNA complexes are indicated on the left of the gel based on shifts in molecular weight.