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PDBsum entry 1opc
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Transcription regulation
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PDB id
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1opc
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References listed in PDB file
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Key reference
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Title
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The DNA-Binding domain of ompr: crystal structures of a winged helix transcription factor.
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Authors
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E.Martínez-Hackert,
A.M.Stock.
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Ref.
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Structure, 1997,
5,
109-124.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: The differential expression of the ompF and ompC genes is regulated
by two proteins that belong to the two component family of signal transduction
proteins: the histidine kinase, EnvZ, and the response regulator, OmpR. OmpR
belongs to a subfamily of at least 50 response regulators with homologous
C-terminal DNA-binding domains of approximately 98 amino acids. Sequence
homology with DNA-binding proteins of known structure cannot be detected, and
the lack of structural information has prevented understanding of many of this
familys functional properties. RESULTS: We have determined the crystal structure
of the Escherichia coli OmpR C-terminal domain at 1.95 A resolution. The
structure consists of three alpha helices packed against two antiparallel beta
sheets. Two helices, alpha2 and alpha3, and the ten residue loop connecting them
constitute a variation of the helix-turn-helix (HTH) motif. Helix alpha3 and the
loop connecting the two C-terminal beta strands, beta6 and beta7, are probable
DNA-recognition sites. Previous mutagenesis studies indicate that the large loop
connecting helices alpha2 and alpha3 is the site of interaction with the alpha
subunit of RNA polymerase. CONCLUSIONS: OmpRc belongs to the family of 'winged
helix-turn-helix' DNA-binding proteins. This relationship, and the results from
numerous published mutagenesis studies, have helped us to interpret the
functions of most of the structural elements present in this protein domain. The
structure of OmpRc could be useful in helping to define the positioning of the
alpha subunit of RNA polymerase in relation to transcriptional activators that
are bound to DNA.
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Figure 6.
Figure 6. Three views of the electrostatic surface
potential of OmpRc. Red indicates a negatively charged region,
blue indicates a positively charged region and white indicates a
neutral or hydrophobic region. (a) The molecule is oriented
similarly to Figure 5b, displaying the positive electrostatic
surface potential of the DNA-binding surface. (b) The molecule
is oriented similarly to Figure 5a. The a loop surface, that may
interact with the a subunit of RNA polymerase, is rather neutral
or hydrophobic. (c) This remarkable, negatively charged face of
the protein lies at the C-terminal end of the recognition helix.
(Figure produced using GRASP [73].)
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The above figure is
reprinted
by permission from Cell Press:
Structure
(1997,
5,
109-124)
copyright 1997.
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