zincfingers
Zinc fingers are small protein structural motifs that coordinate one or more zinc ions to stabilize folds capable of interacting with nucleic acids, proteins, or small molecules. The best-characterized class is the C2H2 zinc finger, in which a zinc ion is coordinated by two cysteines and two histidines. Each finger is typically 28 to 30 amino acids long and folds into a beta-hairpin and an alpha-helix; the recognition helix positions itself in the DNA major groove to contact bases. Multiple fingers arranged in tandem can recognize longer DNA sequences, with specific residues at defined positions making base contacts that determine sequence specificity. Beyond DNA binding, zinc fingers can mediate RNA interactions or protein–protein contacts, and large families of zinc finger proteins function as transcription factors regulating development, differentiation, or metabolism. Other zinc finger subtypes exist, including C4 motifs in some nuclear receptors and less common patterns such as C2HC and treble-clef arrangements.
Zinc finger domains have been leveraged as tools for genome engineering. In the late 1990s and early