Figure 4.
Cancer associated MAX mutants with altered DNA binding property. (A) R36W diminished DNA binding as measured by fluorescence polarization assays. Inset within the box: Sequences of the various modified E-box and control (C-1, C-2 and C-3) DNA substrates used. (B and C) H28R enhanced DNA binding with oligos containing varied forms of cytosine. The estimated dissociation constant KD values are uniformly low in 150 mM NaCl (panel B) but considerably increased in 350 mM NaCl (panel C). Note that the smaller the calculated KD value, the higher the binding affinity. (D) The enhanced DNA binding affinity of H28R might allow the mutant to bind near-cognate sequence. (E) The effect of the R60Q mutation on DNA binding. Despite significant reduction of affinity, 5caC DNA is still preferred over unmodified DNA by the R60Q mutant. Data represent the mean ± SEM of two independent determinations performed in duplicate.