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PDBsum entry 2pee
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Hydrolase inhibitor
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PDB id
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2pee
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References listed in PDB file
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Key reference
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Title
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The n terminus of the serpin, Tengpin, Functions to trap the metastable native state.
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Authors
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Q.Zhang,
A.M.Buckle,
R.H.Law,
M.C.Pearce,
L.D.Cabrita,
G.J.Lloyd,
J.A.Irving,
A.I.Smith,
K.Ruzyla,
J.Rossjohn,
S.P.Bottomley,
J.C.Whisstock.
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Ref.
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EMBO Rep, 2007,
8,
658-663.
[DOI no: ]
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PubMed id
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Abstract
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Serpins fold to a metastable native state and are susceptible to undergoing
spontaneous conformational change to more stable conformers, such as the latent
form. We investigated conformational change in tengpin, an unusual prokaryotic
serpin from the extremophile Thermoanaerobacter tengcongensis. In addition to
the serpin domain, tengpin contains a functionally uncharacterized 56-amino-acid
amino-terminal region. Deletion of this domain creates a
variant--tengpinDelta51--which folds past the native state and readily adopts
the latent conformation. Analysis of crystal structures together with
mutagenesis studies show that the N terminus of tengpin protects a hydrophobic
patch in the serpin domain and functions to trap tengpin in its native
metastable state. A 13-amino-acid peptide derived from the N terminus is able to
mimick the role of the N terminus in stabilizing the native state of
tengpinDelta51. Therefore, the function of the N terminus in tengpin resembles
protein cofactors that prevent mammalian serpins from spontaneously adopting the
latent conformation.
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Figure 1.
Figure 1 Crystal structures of tengpin. (A) Structure of native
tengpin  31.
Elements of secondary structure are labelled. The A  -sheet
is in shown in red; B -sheet
in green; C -sheet
in yellow and  -helices
are in cyan; the reactive centre loop (RCL) is in magenta and
the N-terminal region is shown in purple. Tengpin contains 42 of
the 51 highly conserved residues present in most serpins;
substitutions at these positions are generally conservative. The
number of salt bridges of the surface of tengpin (78) is also
comparable with other mesophilic and thermophilic counterparts
(Fulton et al, 2005). Notably, 21 amino acids of the amino
terminus of the serpin domain could be fully resolved in
electron density; these residues adopt an extended
conformation and form several interactions with the D-helix
(supplementary Table 1 online). (B) Structure of latent tengpin
51.
Colouring as for (A). A structural comparison of the native and
latent conformations of tengpin shows that strands s3A, s2A and
s1A, together with the E- and F-helix, shift to accommodate the
RCL as a fourth strand in the A -sheet.
Conformational changes in strands s3C and s4C are apparent as a
result of the transition to the latent state and the
repositioning of s1C. The shutter region is indicated. (C) The
contacts between the N terminus, helices E, F and A sheet
strands 1 and 2 of tengpin 31.
Side chains from the A-sheet are in red, from -helices
in cyan and from the N terminus in yellow. Dashed lines indicate
hydrogen bonds. (D) Comparison of the binding sites of the N
terminus (purple) and tengpin (left) with that of the
somatomedin B (SMB) domain of vitronectin (purple) and
plasminogen activator inhibitor-1 (PAI-1, right; Zhou et al,
2003).
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Figure 3.
Figure 3 Cartoon of latent tengpin 51
and tengpin 31.
The figure shows how the side chains of residues L41 and M42, in
the native state, protect the hydrophobic pocket formed by
residues L159, I162 and I170.
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The above figures are
reprinted
from an Open Access publication published by Macmillan Publishers Ltd:
EMBO Rep
(2007,
8,
658-663)
copyright 2007.
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