zinc finger

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zinc finger A structural motif characteristic of certain proteins that bind to DNA, notably transcription factors. It consists of a finger-like fold of amino acids at the base of which lie two cysteine and two histidine residues. These four residues bind a single zinc ion in a tetrahedral array. The finger interacts with about five base pairs in the nucleic acid molecule. Unlike other DNA-binding motifs, such as the helix-turn-helix and the leucine zipper, the zinc finger is also found in proteins that bind to RNA, such as RNA-directed RNA polymerase.