COMPARISON OF THE FREE AND DNA-COMPLEXED FORMS OF THE DNA-BINDING DOMAIN FROM C-MYB

The DNA-binding domain of c-Myb consists of three imperfect tandem rep eats (R1, R2 and R3). The three repeats have similar overall architect ures. each containing a helix-turn-helix variation motif. The three co nserved tryptophans in each repeat participate in forming a hydrophobi c core. Comparison of the three repeat structures indicated that cavit ies are found in the hydrophobic core of R2, which is thermally unstab le. On complexation with DNA, the orientations of R2 and R3 are fixed by tight binding and their conformations;ire slightly changed. No sign ificant changes occur in the chemical shifts of R1 consistent with its loose interaction with DNA.