-  Class
-  C6 zinc cluster factors
-  "TRANSFAC class description C0005: Zinc finger motif of GAL4-type. Present to date in many fungal regulators. The proteins are typically, though not exclusively transcriptional activators. Six cysteine residues coordinate two zinc ions, i. e. two of the thiol groups coordinate two zinc ions (six cysteines binuclear cluster DNA-binding domain). All GAL4-type proteins possess a single N-terminal zinc finger with an adjacent basic region, which is critical for sequence-specific recognition. Each C3-repeat unit of the structural motif of six cysteines forms short alpha-helical structures separated by a loop with a proline-associated turn. A number of zinc cluster proteins contain leucine zipper-like heptad repeat motifs C-terminal to the zinc-cluster. These motifs have been shown to form coiled-coil structures involved in protein-protein interactions (often homodimerization). The GAL-4 protein binds as a dimer to DNA sites characterized by the presence of two CGG triplets separated by 11 base pairs. The zinc(II)-binding cluster lies in the DNA major groove and contacts three base pairs."