Schematic diagram of a C2H2 zinc-finger motif. The paired cysteines (C) and histidines (H) that bind the zinc ion are shown in yellow and blue, respectively. The linker sequence, shown in green with its consensus sequence in the single-letter amino acid code, frequently joins adjacent fingers. This is apparent in the lower panel, which shows the typical arrangement of fingers in a C2H2 ZNF protein. The two large hydrophobic residues, which are also structurally important, are shown in red. The black residues are not structurally important and include those responsible for contacting DNA during sequence-specific binding . The precise number of 'black' residues between the cysteines, histidines and on the loop may vary .