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PDBsum entry 1us6
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Transcription repressor
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PDB id
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1us6
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References listed in PDB file
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Key reference
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Title
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Crystal structure of the quorum-Sensing protein tram and its interaction with the transcriptional regulator trar.
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Authors
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A.Vannini,
C.Volpari,
S.Di marco.
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Ref.
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J Biol Chem, 2004,
279,
24291-24296.
[DOI no: ]
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PubMed id
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Abstract
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Transfer of the tumor-inducing plasmid in Agrobacterium tumefaciens is
controlled by a quorum-sensing system whose main components are the
transcriptional regulator TraR and its autoinducer. This system allows bacteria
to synchronize infection of the host plant when a "quorum" of cells
has been reached. TraM is an A. tumefaciens protein involved in the regulation
of this system because it binds to TraR and prevents it from binding DNA. As a
first step to understanding the molecular basis for the regulation of TraR by
TraM, we have determined the crystal structure of TraM at 1.65 A resolution.
This protein is packed as a dimer, with each monomer consisting mainly of two
antiparallel alpha helices. Monomers are tightly associated, with a large
hydrophobic area buried upon dimerization. Secondly, we characterized the
TraR-TraM complex in vitro. TraM (11.4 kDa, monomer molecular mass) binds
tightly TraR (27 kDa, monomer molecular mass) forming a stable oligomeric
complex that likely accounts for two TraR and two TraM dimers.
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Figure 2.
FIG. 2. A, ribbon diagrams of the TraM dimer. Mutants that
have demonstrated a reduction in TraR binding efficiency, as
well as a loss of activity in vivo, are drawn in stick
representation (Leu-29, His-40, Arg-41, Leu-54, Tyr-72, Val-86,
Gly-94, and Pro-97). Oxygen, carbon, and nitrogen are colored
red, gray, and blue, respectively. Only one monomer is labeled,
for clarity. Three orthogonal views are shown. B, molecular
surface of the TraM dimer with mutants Leu-29 (orange), His-40
(white), Arg-41 (green), Leu-54 (red), Tyr-72 (blue), Val-86
(cyan), Gly-94 (magenta), and Pro-97 (yellow) mapped on. Only
one monomer is labeled, for clarity. Three orthogonal views are
shown.
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Figure 4.
FIG. 4. A, schematic model of a two-dimers-to-two-dimers
TraR-TraM complex. For clarity, just the TraR DNA binding domain
(TraR DBD) is depicted. Red arrows represent the 2-fold axes of
each TraR and TraM dimer. Two views are shown. B, molecular
surface of the hypothetical TraR-TraM complex. The red filled
circles indicate the putative position of an N-terminal His tag
on TraM.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2004,
279,
24291-24296)
copyright 2004.
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