Structure of the PHD Zinc Finger from Human Williams-Beuren Syndrome Transcription Factor

The PHD (plant homeo domain) is a ∼50-residue motif found mainly in proteins involved in eukaryotic transcription regulation. The characteristic sequence feature is a conserved Cys4-HisCys3 zinc binding motif. We have determined the solution structure of the PHD motif from the human Williams-Beuren syndrome transcription factor (WSTF) protein. The domain folds into an interleaved zinc finger which binds two Zn2+ in a similar manner to that of the RING and FYVE domains. The structure reveals a conserved zinc-binding core, together with two variable loops that are likely candidates for interactions between the various PHD domains and their specific ligands.