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PDBsum entry 2bsh
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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 yersinia enterocolitica type III secretion chaperone syct.
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Authors
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C.R.Büttner,
G.R.Cornelis,
D.W.Heinz,
H.H.Niemann.
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Ref.
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Protein Sci, 2005,
14,
1993-2002.
[DOI no: ]
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PubMed id
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Abstract
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Pathogenic Yersinia species use a type III secretion (TTS) system to deliver a
number of cytotoxic effector proteins directly into the mammalian host cell. To
ensure effective translocation, several such effector proteins transiently bind
to specific chaperones in the bacterial cytoplasm. Correspondingly, SycT is the
chaperone of YopT, a cysteine protease that cleaves the membrane-anchor of
Rho-GTPases in the host. We have analyzed the complex between YopT and SycT and
determined the structure of SycT in three crystal forms. Biochemical studies
indicate a stoichometric effector/chaperone ratio of 1:2 and the
chaperone-binding site contains at least residues 52-103 of YopT. The crystal
structures reveal a SycT homodimer with an overall fold similar to that of other
TTS effector chaperones. In contrast to the canonical five-stranded
anti-parallel beta-sheet flanked by three alpha-helices, SycT lacks the
dimerization alpha-helix and has an additional beta-strand capable of undergoing
a conformational change. The dimer interface consists of two beta-strands and
the connecting loops. Two hydrophobic patches involved in effector binding in
other TTS effector chaperones are also found in SycT. The structural similarity
of SycT to other chaperones and the spatial conservation of effector-binding
sites support the idea that TTS effector chaperones form a single functional and
structural group.
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Figure 2.
Figure 2. SycT lacks the dimerization helix  2. Ribbon
models of Yersinia enterocolitica SycT, Yersinia
pseudotuberculosis SycE (PDB identifier 1L2W [PDB]
; Birtalan et al. 2002), Salmonella typhimurium SicP (1JYO;
Stebbins and Galan 2001), Salmonella enterica SigE (1K3S; Luo et
al. 2001), Yersinia pestis SycH (1TTW; Phan et al. 2004),
Pseudomonas syringae pv. phaseolicola AvrPphF ORF1 (1S28; Singer
et al. 2004), and Shigella flexneri Spa15 (1R9Y; Van Eerde et
al. 2004). The monomers in a dimer are colored blue and red. The
helices 2 are
highlighted in orange and turquoise.
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Figure 3.
Figure 3. Cavity in the SycT dimerization interface. A
polar cavity is enclosed in the dimerization interface of SycT
(crystal form #1, cavity as pink surface model and blue side
chains of residues Trp47, Pro70, Ala71, His72, Val73, Leu83,
Trp84, Ser85, and Ser88, and red side chain for Gln86). Both
Val90 residues (green) shield the cavity from the outside. In
contrast, the cavity in SycH is accessible and possesses a
positive charge (Arg80, red side chain).
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The above figures are
reprinted
by permission from the Protein Society:
Protein Sci
(2005,
14,
1993-2002)
copyright 2005.
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