User:Wayne Decatur/Gal 4
From Proteopedia
Gal4p is a transcriptional activator in Saccharomyces cerevisiae that regulates the expression of genes to coordinate the response to the carbon source galactose.
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Background
Gal4p is a transcriptional activator in Saccharomyces cerevisiae that regulates the expression of genes to coordinate the response to the carbon source galactose. Gal4p is an 881-amino-acid protein with a Zn cluster-type DNA-binding domain, a linker domain, a dimerization domain, and two acidic activation domains. The structure of the DNA-binding domain(1d66), the dimerization domain (1hbw), and the activation domain (3bts) has been solved separately. There is a structure of the DNA-binding and dimerization domains as one unit as well (3coq).
Pioneering studies on Gal4p from the Ptashne laboratory shaped our understanding of transcriptional activation in eukaryotes, and Gal4p derivatives, along with their cognate promoters, continue to be used as tools by investigators preforming research in yeast.
DNA Recognition by Gal4p
The protein binds as a dimer to a symmetrical 17-base-pair sequence. Specifically, the consensus Gal4p-binding site is a 17-mer of sequence conforming to the motif below.
5'-CGGNNNNNNNNNNNCCG-3'
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3'-CGGNNNNNNNNNNNGGC-5'
The DNA binding domain uses four Cys residues to coordinate the binding of two ions of zinc (Zn(II)). In the crystal structure the zinc ions are represented by other members of the same group on the periodic table, the heavier cadmium ions. The Zn-binding motif lets the structure accomplish more with fewer amino acids, the metals lending an "economy of structure", arranging two helices to recognize a specific DNA site.
Reference
- Marmorstein R, Carey M, Ptashne M, Harrison SC. DNA recognition by GAL4: structure of a protein-DNA complex. Nature. 1992 Apr 2;356(6368):408-14. PMID:1557122 doi:http://dx.doi.org/10.1038/356408a0
