Zinc Finger Protein with DNA (1zaa) - Zinc finger proteins bind to DNA and function as transcription factors. When bound to promoters they turn on transcription. In the illustration below, a protein from mouse having three zinc fingers is shown. The "fingers" are regions of alpha helix (shown in pink) that are situated in the groves of the of DNA (illustrated here as 2 sets of coiled white lines). In addition to containing amino acids that interact specifically with bases in the DNA, each finger also contains two histidine residues having their R-groups pointing away from the DNA. In the loop region adjacent to each finger (blue and yellow) there are two cysteines with their R-groups pointing toward the alpha helix. Between the histidines and cysteines is a zinc ion (Zn 2+) which helps to stabilize the tertiary structure of the protein. Some zinc finger proteins coordinate the zinc ion between 4 cysteines residues. This mouse protein contains 3 fingers but some have as few as 2 to as many as 9 zinc fingers. The length of the binding site within the DNA varies accordingly.

8/22/04 Copyright (C) 2004, Jonathan Monroe, monroejd@jmu.edu. All rights reserved.
URL: http://csm.jmu.edu/biology/courses/bio220/zincfin.html