Effects of DNA binding and metal substitution on the dynamics of the GAL4 DNA‐binding domain as studied by amide proton exchange

Abstract

Backbone amide proton exchange rates in the DNA‐binding domain of GAL4 have been determined using 1H–15N heteronuclear correlation NMR spectroscopy. Three forms of the protein were studied — the native Zn‐containing protein, the Cd‐substituted protein, and a Zn‐GAL4/DNA complex. Exchange rates in the Zn‐containing protein are significantly slower than in the Cd‐substituted protein. This shows that Cd‐substituted GAL4 is destabilized relative to the native Zn‐containing protein. Upon DNA binding, global retardation of amide proton exchange with solvent was observed, indicating that internal fluctuations of the DNA‐recognition module are significantly reduced by the presence of DNA. In all forms of the protein, the internal dyad symmetry of the DNA‐recognition module of GAL4 is reflected by the backbone amide proton exchange rates. Copyright © 1992 The Protein Society