MoBio Zinc Finger Chapter 4

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, C4, and C6.

C2H2 zinc finger:

It is characterized by the sequence CX2-4C....HX2-4H, 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.

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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.

C4 zinc finger:

Its consensus sequence is CX2CX13CX2CX14-15CX5CX9CX2C. The first four cysteine residues bind to a zinc ion and the last four cysteine residues bind to another zinc ion.

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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.

C6 zinc finger.

It has the consensus sequence CX2CX6CX5-6CX2CX6C. The yeast's Gal4 contains such a motif where six cysteine residues interact with two zinc ions.

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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.