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PDBsum entry 2v6l
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Protein transport
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PDB id
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2v6l
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References listed in PDB file
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Key reference
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Title
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Molecular model of a type III secretion system needle: implications for host-Cell sensing.
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Authors
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J.E.Deane,
P.Roversi,
F.S.Cordes,
S.Johnson,
R.Kenjale,
S.Daniell,
F.Booy,
W.D.Picking,
W.L.Picking,
A.J.Blocker,
S.M.Lea.
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Ref.
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Proc Natl Acad Sci U S A, 2006,
103,
12529-12533.
[DOI no: ]
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PubMed id
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Abstract
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Type III secretion systems are essential virulence determinants for many
Gram-negative bacterial pathogens. The type III secretion system consists of
cytoplasmic, transmembrane, and extracellular domains. The extracellular domain
is a hollow needle protruding above the bacterial surface and is held within a
basal body that traverses both bacterial membranes. Effector proteins are
translocated, via this external needle, directly into host cells, where they
subvert normal cell functions to aid infection. Physical contact with host cells
initiates secretion and leads to formation of a pore, thought to be contiguous
with the needle channel, in the host-cell membrane. Here, we report the crystal
structure of the Shigella flexneri needle subunit MxiH and a complete model for
the needle assembly built into our three-dimensional EM reconstruction. The
model, combined with mutagenesis data, reveals that signaling of host-cell
contact is relayed through the needle via intersubunit contacts and suggests a
mode of binding for a tip complex.
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Figure 2.
Fig. 2. Docking of the atomic model of MxiH into the EM
density of the Shigella T3SS needle. (A) Molecule A of MxiH
(ribbon) with the modeled N-terminal helix (cylinder) is shown
as two views rotated by 90° about the long axis of the
molecule. (B) End-on view of a 40-Å-thick section of the
assembled needle. Each MxiH monomer is shown as in A and colored
differently, starting from red and circling the needle to
purple. EM density is shown as a blue mesh. (C) Stereo diagram
of the side view of the assembled needle, colored as for B. Note
that B and C are not shown at the same scale, and the needle
assembly has an exterior diameter of  70 Å (16).
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Figure 4.
Fig. 4. Characterization of the putative tip-interaction
interface of a T3SS needle. (A) Surface representation of the
side view of the T3SS needle with each monomer colored
differently, starting from red and circling the needle to
purple. Residues likely to effect interactions with the tip
complex are highlighted as follows: P44 and Q51 in Shigella
(white) and the equivalent of D46 in Yersinia (gray). (B) View
and coloring as for A, with residues conserved between Shigella
MxiH and Yersinia YscF highlighted. Residues conserved in the
head domain: L37, P41, N43, P44, L46, L47, A48, and Q51 (white);
in the tail domain, N62, S65, V68, K72, D73, I78, Q80, and F82
(gray) are shown for the top circle of the needle. (C Left)
Ribbon diagram of LcrV (30) colored N (blue) to C (red) termini.
(C Right) Overlay of the C-terminal helices of MxiH (red,
residues 45–75) and LcrV (blue, residues 287–317), with all
but the overlaid region made transparent to aid visualization.
(D) Model of an LcrV tip complex (surface representation, gray)
onto the tip of a T3SS needle.
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Secondary reference #1
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Title
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Helical structure of the needle of the type III secretion system of shigella flexneri.
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Authors
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F.S.Cordes,
K.Komoriya,
E.Larquet,
S.Yang,
E.H.Egelman,
A.Blocker,
S.M.Lea.
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Ref.
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J Biol Chem, 2003,
278,
17103-17107.
[DOI no: ]
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PubMed id
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Figure 2.
Fig. 2. Comparison of XRFD image from oriented needle
samples and EM power spectrum. A, half of the central region of
x-ray fiber diffraction pattern from aligned mxiH^  /mxiH^+++
long needles taken at station 14.2 of the SRS Daresbury (see
"Experimental Procedures"). B, half of the averaged power
spectrum generated from 5402 partially overlapping segments
extracted from images of 108 negatively stained mxiH^ /mxiH^+++
long needles. For both images, the peaks corresponding to
specific layer lines are indicated with the layer line spacings
and indices (as determined as in text) shown. C, XRFD pattern as
shown in A but displaying the high resolution layer lines
discussed in the text.
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Figure 4.
Fig. 4. Various views of the three-dimensional
reconstruction. All of the images were produced using AESOP (a
program developed by M. E. M. Noble). A and B, show a top view
and side view, respectively, of the three-dimensional
reconstruction of the Shigella flexneri needles obtained as
described under "Results." The electron density is thresholded
as described in the text to generate the solid surface. C,
composite image giving a model for the structure of the needle
complex in the bacterial membranes using the needle
reconstruction presented here in combination with the earlier
reconstruction of the basal body of the needle complex (9).
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The above figures are
reproduced from the cited reference
with permission from the ASBMB
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Headers
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