Solution structure of a zinc finger domain of yeast ADR1.

The "zinc finger" is a 30-residue repeating motif that has been identified in a variety of eukaryotic transcription factors. Each domain is capable of binding a Zn2+ ion through invariant Cys and His residues. We have determined the three-dimensional structure of a synthetic peptide that corresponds to one of the two zinc finger domains in the yeast transcription factor ADR1, using two-dimensional nuclear magnetic resonance spectroscopy. The Zn2(+)-bound structure of the peptide consists of a loop containing the two Cys residues, a "fingertip," a 12- to 13-residue alpha-helix containing the two His residues, and a C-terminal tail. A majority of the interresidue contacts observed involve the seven conserved residues of the prototypic zinc finger (i.e., the four zinc ligands and the three hydrophobic residues), indicating that these residues are largely responsible for the three-dimensional structure of the domain and that all the zinc finger domains of the TFIIIA class will have similar structures. Potential DNA-binding residues are found throughout the structure, with the highest concentration of such residues on the external face of the alpha-helix.