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PDBsum entry 2ebh
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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 structures reveal a thiol protease-Like catalytic triad in the c-Terminal region of pasteurella multocida toxin.
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Authors
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K.Kitadokoro,
S.Kamitani,
M.Miyazawa,
M.Hanajima-Ozawa,
A.Fukui,
M.Miyake,
Y.Horiguchi.
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Ref.
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Proc Natl Acad Sci U S A, 2007,
104,
5139-5144.
[DOI no: ]
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PubMed id
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Abstract
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Pasteurella multocida toxin (PMT), one of the virulence factors produced by the
bacteria, exerts its toxicity by up-regulating various signaling cascades
downstream of the heterotrimeric GTPases Gq and G12/13 in an unknown fashion.
Here, we present the crystal structure of the C-terminal region (residues
575-1,285) of PMT, which carries an intracellularly active moiety. The overall
structure of C-terminal region of PMT displays a Trojan horse-like shape,
composed of three domains with a "feet"-,"body"-, and
"head"-type arrangement, which were designated C1, C2, and C3 from the
N to the C terminus, respectively. The C1 domain, showing marked similarity in
steric structure to the N-terminal domain of Clostridium difficile toxin B, was
found to lead the toxin molecule to the plasma membrane. The C3 domain possesses
the Cys-His-Asp catalytic triad that is organized only when the Cys is released
from a disulfide bond. The steric alignment of the triad corresponded well to
that of papain or other enzymes carrying Cys-His-Asp. PMT toxicities on target
cells were completely abrogated when one of the amino acids constituting the
triad was mutated. Our results indicate that PMT is an enzyme toxin carrying the
cysteine protease-like catalytic triad dependent on the redox state and
functions on the cytoplasmic face of the plasma membrane of target cells.
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Figure 4.
Fig. 4. Dynamic alterations in the loop[H28-H29] upon
breakage of the disulfide bond. (A–C) The loop[H28-H29] and
the proximal regions in C-PMT (A), C-PMT[1159S] (B), and
C-PMT[1165S] (C) are shown. A  [A]-weighted omit
electron density map (contoured at 3 ) is superimposed on
the stick model of key residues, Cys^1159 (Ser^1159 in B),
Cys^1165 (Ser^1165 in C), His^1205, Asp^1220, and Gln^1225. (D)
Comparison of the active sites among C-PMT[1159S] (light green)
and C-PMT[1165S] (light blue) with papain (pink), AvrPphB (lime
green), and N-acetyltransferase (orange). His^1205, Asp^1220,
and Cys^1165 of C-PMT[1159S] were superimposed on the
corresponding residues of the counterpart proteins by Lsqkab in
the CCP4 program suite (30).
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Figure 5.
Fig. 5. Model of the domain architecture of
membrane-associated C-PMT. A ribbon diagram of C-PMT[1159S] is
presented. The C1, C2, and C3 domains are in blue, green, and
magenta, respectively. Note that the membrane-targeting region
in the C1 domain (yellow oval) and the catalytic cleft in the C3
domain (red oval) reside on the same face of the molecule, which
faces the cytoplasmic surface of the membrane.
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