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PDBsum entry 1xkp
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Membrane protein/chaperon
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PDB id
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1xkp
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Contents |
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231 a.a.
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121 a.a.
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126 a.a.
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References listed in PDB file
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Key reference
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Title
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Three-Dimensional structure of a macromolecular assembly that regulates type III secretion in yersinia pestis.
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Authors
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F.D.Schubot,
M.W.Jackson,
K.J.Penrose,
S.Cherry,
J.E.Tropea,
G.V.Plano,
D.S.Waugh.
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Ref.
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J Mol Biol, 2005,
346,
1147-1161.
[DOI no: ]
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PubMed id
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Abstract
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Yersinia pestis, the causative agent of plague, utilizes a type III secretion
system (T3SS) to inject effector proteins directly into the cytosol of mammalian
cells where they interfere with signal transduction pathways that regulate actin
cytoskeleton dynamics and inflammation, thereby enabling the bacterium to avoid
engulfment and destruction by macrophages. Type III secretion normally does not
occur in the absence of close contact with eukaryotic cells. Negative regulation
is mediated in part by a multiprotein complex that has been proposed to act as a
physical impediment to type III secretion by blocking the entrance to the
secretion apparatus prior to contact with mammalian cells. This complex is
composed of YopN, its heterodimeric secretion chaperone SycN-YscB, and TyeA.
Here, we report two crystal structures of YopN in complex with its heterodimeric
secretion chaperone SycN-YscB and the co-regulatory protein TyeA, respectively.
By merging these two overlapping structures, it was possible to construct a
credible theoretical model of the YopN-SycN-YscB-TyeA complex. The modeled
assembly features the secretion signaling elements of YopN at one end of an
elongated structure and the secretion regulating TyeA binding site at the other.
A patch of highly conserved residues on the surface of the C-terminal
alpha-helix of TyeA may mediate its interaction with structural components of
the secretion apparatus. Conserved arginine residues that reside inside a
prominent cavity at the dimer interface of SycN-YscB were mutated in order to
investigate whether they play a role in targeting the YopN-chaperone complex to
the type III secretion apparatus. One of the mutants exhibited a phenotype that
is consistent with this hypothesis.
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Figure 1.
Figure 1. (a) Two orthogonal views showing the ribbon model
of the ternary complex between YopN and its heterodimeric
secretion chaperone SycN–YscB. YopN, SycN and YscB are
represented in cyan, orange and yellow, respectively. The broken
line between YopN residues Thr57 and Glu65 denotes the
disordered region of the CBD. This Figure was generated by
PYMOL^51 (http://www.pymol.org). (b) Structure of the
YopN^76-293–TyeA complex. YopN and TyeA are depicted in cyan
and red, respectively. Helices α-1 and α-3 of TyeA surround
helix α-12 of YopN to form the bulk of the intermolecular
interface.
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Figure 6.
Figure 6. A model of the YopN–SycN–YscB–TyeA complex
constructed by merging the two overlapping crystal structures.
The RMSD of only 1 Å between the YopN molecules in the two
structures allowed the construction of the model, which in all
likelihood depicts the assembly as it exists in the Y. pestis
cytoplasm. Noteworthy are the seeming rigidity of the structure
and the spatial separation of secretion targeting and secretion
regulating elements.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2005,
346,
1147-1161)
copyright 2005.
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Secondary reference #1
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Title
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A pivotal role for reductive methylation in the de novo crystallization of a ternary complex composed of yersinia pestis virulence factors yopn, Sycn and yscb.
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Authors
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F.D.Schubot,
D.S.Waugh.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2004,
60,
1981-1986.
[DOI no: ]
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PubMed id
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Figure 3.
Figure 3 2F[o] - F[c] Fourier map of electron density contoured
at 1.5 [74][sigma] for (a) Gly32, the methylated amino-terminus
of YopN, and (b) YopN residue Lys237. These two residues
represent the only places where the added methyl groups were
clearly visible. This figure was generated by PyMOL (DeLano,
2001[75] [DeLano, W. L. (2001). PyMOL. DeLano Scientific, LLC,
San Carlos, CA, USA.]-[76][bluearr.gif] ).
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Figure 4.
Figure 4 Electron density of a [99][sigma] -weighted 2F[o] -
F[c] Fourier map contoured at 1.5 [100][sigma] for Lys77 of
YscB, the only unmethylated lysine residue in the ternary
complex, which interacts with acidic residues from both YopN and
SycN. This observation is important because it demonstrates that
the experimental conditions of reductive methylation leave such
intermolecular contact sites unaffected.
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The above figures are
reproduced from the cited reference
with permission from the IUCr
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