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Title
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The function and structure of the metal coordination sites within the glucocorticoid receptor DNA binding domain.
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Authors
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L.P.Freedman,
B.F.Luisi,
Z.R.Korszun,
R.Basavappa,
P.B.Sigler,
K.R.Yamamoto.
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Ref.
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Nature, 1988,
334,
543-546.
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PubMed id
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Abstract
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The glucocorticoid receptor enhances or represses transcription by binding to
specific DNA sequences termed glucocorticoid response elements, or GREs. Studies
of cloned glucocorticoid receptors reveal that the protein is organized as
functional domains, in an arrangement that appears to be common among members of
the steroid receptor family. A segment near the centre of the gene specifies DNA
binding activity in vitro and contains two sequence motifs similar to 'zinc
fingers' found in Xenopus transcription factor IIIA (TFIIIA). Such sequence
motifs have been identified in nucleic acid binding proteins from a wide range
of organisms. Steroid receptor protein fingers are proposed to bind zinc through
two pairs of conserved cysteine residues. We report here that a protein of
relative molecular mass 19,000 (Mr = 19 K) encompassing the DNA-binding domain
of the glucocorticoid receptor that has been overexpressed in Escherichia coli
and purified to homogeneity reversibly ligates two Zn(II) or Cd(II) ions. We
show that metal ions are required for specific DNA binding and proper folding.
Using EXAFS (extended X-ray absorption fine structure) and visible light
spectroscopies, we find that each Zn atom is coordinated in a tetrahedral
arrangement by four cysteines.
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