Zinc finger protein

A zinc finger protein is a DNA-binding protein domain consisting of zinc fingers ranging from two in the Drosophila regulator ADR1, the more common three in mammalian Sp1 up to nine in TFIIIA. They occur in nature as the part of transcription factors conferring DNA sequence specificity as the DNA-binding domain.

They have also found use in protein engineering due to their modularity and have prospects as components of tools for use in therapeutic gene modulation and zinc finger nucleases.

Structure
Zinc finger protein consists of anti-parallel hairpin motif. It consists of 2 beta strands, one alpha helix and a hairpin structure. The first Zn binds to Cys-3 of 1st beta strand, second Zn binds to Cys-6 that is present in the tight loop that separates the two beta strands. The other two Zn is coordinated to Cys 19 & 23 which are present in C-terminal half of the alpha helix. The hairpin is followed by alpha helix of about 3.5 turns. The binding of Zn at the last two positions mentioned causes distortion in alpha helix between these positions to form a 3-10 complex in which H bonding occurs between 1st and 3rd amino acid instead of 1-4 amino acid bonding. Zn in buried in the interior of the protein and is necessary for the formation of a stable finger structure in aqueous solution. The zinc does not interact with DNA.