Zinc finger

Zinc finger proteins are a class of nucleic acid binding proteins that have a specific protein domain: the zinc finger domain, in which a zinc ion ( Zn2 ) is coordinated. The polypeptide chain takes through the incorporation of the zinc atom is a loop-shaped structure - the so-called zinc finger - one which can specifically interact with the DNA or RNA. They were discovered by Aaron Klug in the transcription factor IIIA from Xenopus laevis Krallenfroschart.

Construction

Zinc finger proteins have at least one zinc finger domain that folds around a central zinc ion ( see figure). In this case, the zinc ion formed by its filled d orbital shell strong interactions with sulfur, nitrogen or oxygen atoms of the amino acid residues (generally cysteine ​​and histidine). Here, there is constructed a tetrahedral coordinative bond. The zinc ion is also responsible for ensuring that even relatively small portions of a polypeptide bond are stabilized so that they can interact with nucleic acids. Since zinc has only one stable oxidation state, it may also do not catalyze undesirable reactions within the cell. The zinc finger domain is a domain mainly binding to DNA, thus the zinc finger proteins are most transcription factors. RNA -binding zinc finger proteins are known. The zinc finger proteins, but can also include receptors for steroid hormones.

In the role as a transcription factor, the loop of the protein, which contains in the interior of each of two cysteine ​​and two histidine residues of the central Zn2 ion ( Cys2His2 zinc finger protein) binds to a specific base in the major groove of the DNA double helix. Zinc finger proteins can also be composed of four or six zinc binding cysteine ​​residues ( or Cys6 Cys4 zinc finger proteins).

The zinc finger domain is always consists of a consensus sequence, which may vary depending on the nature of the zinc finger domain.

Potential applications

The ability of zinc finger proteins bind specifically to virtually any DNA sequence makes, specially built (designed ) zinc finger proteins with potential gene therapeutics for the treatment of various genetic diseases. It can be produced with zinc finger domains artificial restriction enzymes Zinkfingernukleasen.