Zinc Finger

The zinc finger motif contains one or more zinc ions which are crucial for the structural stability. It can be divided into three types:

C₂H₂ zinc finger:  It is characterized by the sequence CX_2-4C....HX_2-4H, where C = cysteine, H = histidine, X = any amino acid.  In the 3D structure, two cysteine residues and two histidine residues interact with a zinc ion (Figure 4-F-1). 

C₄ zinc finger:  Its consensus sequence is CX₂CX₁₃CX₂CX_14-15CX₅CX₉CX₂C.  The first four cysteine residues bind to a zinc ion and the last four cysteine residues bind to another zinc ion (Figure 4-F-2).

C₆ zinc finger.  It has the consensus sequence CX₂CX₆CX_5-6CX₂CX₆C.  The yeast's Gal4 contains such a motif where six cysteine residues interact with two zinc ions (Figure 4-F-3).

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Figure 4-F-1.  (a) The domain organization of Sp1 which consists of 696 residues.  Locations of zinc finger regions are indicated.  (b) The structure of a zinc finger region.  PDB ID = 1SP1.

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Figure 4-F-2.  (a) The domain organization of the estrogen receptor (ER).  (b) The complex of the ER's zinc finger domain and DNA.  In this figure, two ERs form a dimer.  Each ER binds to two zinc ions (represented by orange balls).  Most steroid hormone receptors contain such motif.  PDB ID = 1HCQ.

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Figure 4-F-3.  (a) The domain organization of Gal4.  (b) Structure of Gal4's zinc finger.  Like many other transcription factors, Gal4 form a dimer to interact with DNA.  In each Gal4, six cysteine residues bind to two zinc ions (represented by orange balls).  PDB ID = 1D66.

Review Articles:

Yeast Gal4: a transcriptional paradigm revisited - EMBO reports, 2006.

GATA1 Function, a Paradigm for Transcription Factors in Hematopoiesis - Mol. Cell Biology, 2004.

The Zinc Finger-containing Transcription Factors GATA-4, -5, and -6 - J. Biol. Chem., 2000.

Krüppel-like Factors: Three Fingers in Many Pies - J. Biol. Chem., 2001.