Zinc-finger domains. A DNA-binding domain comprising three Cys2His2 zinc-finger domains (shown in yellow, blue, and red) is shown in a complex with DNA. Each zinc-finger domain is stabilized by a bound zinc ion (shown in green) through interactions with two cysteine residues and two histidine residues. Notice how the protein wraps around the DNA in the major groove.
[Drawn from 1AAY.pdb.]