A motif of which seven or more may appear in a DNA-binding protein. Each is characterised by two closely spaced cysteine and two histidine residues that serve as ligands for a single Zn²⁺. When bound to Zn²⁺ they form a module from which protrude amino acid side chains that interact with the bases partially exposed to the DNA major groove. Since in the area of contact there is a limited and local parallel of DNA and protein sequences, the occurrence of the contacting amino acid residues in the protein sequence falls into a regularity, or register, that creates in the protein a syllabicity.