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PDBsum entry 1jti
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Loop-Inserted and thermostabilized structure of p1-P1' Cleaved ovalbumin mutant r339t.
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Authors
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M.Yamasaki,
Y.Arii,
B.Mikami,
M.Hirose.
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Ref.
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J Mol Biol, 2002,
315,
113-120.
[DOI no: ]
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PubMed id
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Abstract
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Ovalbumin is a member of a superfamily of serine proteinase inhibitors, known as
the serpins. It is, however, non-inhibitory towards serine proteinases, and
lacks the loop insertion mechanism common to the serpins due to unknown
structural factors. Mutant ovalbumin, R339T, in which the P14 hinge residue is
replaced, was produced and analyzed for its thermostability and
three-dimensional structure. Differential scanning calorimetry revealed that the
mutant ovalbumin, but not the wild-type protein, undergoes a marked
thermostabilization (DeltaT(m)=15.8 degrees C) following the P1-P1' cleavage.
Furthermore, the crystal structure, solved at 2.3 A resolution, clearly proved
that the P1-P1' cleaved form assumes the fully loop-inserted conformation as
seen in serpin that possess inhibitory activity. We therefore conclude that
ovalbumin acquires the structural transition mechanism into the loop-inserted,
thermostabilized form by the single hinge mutation. The mutant protein does not,
however, possess inhibitory activity. The solved structure displays the
occurrence of specific interactions that may prevent the smooth motion, relative
to sheet A, of helices E and F and of the loop that follows helix F. These
observations provide crucial insights into the question why R339T is still
non-inhibitory.
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Figure 2.
Figure 2. Stereo diagrams of P1-P1' cleaved R339T
structure. (a) C^a plots of the P1-P1' cleaved R339T. The
a-helices and b-strands are shown in green and yellow,
respectively. The b-strand, shown in orange, represents the
inserted strand 4A. The Figures were produced with MOLSCRIPT[28]
and Raster3D. [29] (b) Electron density map (2F[o] -F[c]
contoured at 1s) of sheet A. The main chain hydrogen bonds with
a donor-acceptor distance less than 3.3 Å are shown by red
broken lines.
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Figure 4.
Figure 4. Interactions of helix F and its descending loop
with sheet A. C^a traces for (a) intact egg white ovalbumin and
for (b) P1-P1' cleaved R339T are shown in white except that the
reactive center loop or inserted b-strand is represented in
orange. The main chain atoms involved in hydrogen bonds are
shown in the standard colors. The side-chain groups of Arg104,
Trp148, Lys290 and Gln325 are shown in red, yellow, blue and
green, respectively. The indole plane of Trp148 and the plane
formed by the N  epsilon
, C^z, Nr1, and Nr2 atoms of Arg104 intersect with dihedral
angles of 12.7 ° and 10.2 ° in the intact and cleaved
forms, respectively. The shortest distance between the two
planes are 3.3 Å for the Arg104-Nr1 to Trp148-N1 distance
in intact ovalbumin and 3.1 Å for the Arg104-Nr1 to
Trp148-C^d1 distance in cleaved R339T.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2002,
315,
113-120)
copyright 2002.
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