Amino acid substitutions in a long flexible sequence influence thermodynamics and internal dynamic properties of winged helix protein genesis and its DNA complex

The hepatocyte nuclear factor (HNF)-3 homologous DNA binding domain is a highly conserved motif that contains a well-folded helix-turn-helix motif and two highly dynamic wings. Although the function and the properties of this motif have been intensively studied, the role of the internal wing (wing 1) is not well understood. In this study, amino acid substitutions were introduced into wing 1 of a conserved HNF-3 homologous protein, Genesis, and heteronuclear NMR, circular dichroism, DNA gel-shift assay, and fluorescent methods were employed to study and compare the properties of both wild-type and variant Genesis proteins. The data indicate that even though the substitutions are located on a dynamic wing outside the hydrophobic core sequences, they still globally influence biophysical properties of DNA-free Genesis and its DNA complex.