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PDBsum entry 1uhg
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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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Crystal structure of s-Ovalbumin as a non-Loop-Inserted thermostabilized serpin form.
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Authors
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M.Yamasaki,
N.Takahashi,
M.Hirose.
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Ref.
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J Biol Chem, 2003,
278,
35524-35530.
[DOI no: ]
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PubMed id
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Abstract
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Ovalbumin, a non-inhibitory member of serine proteinase inhibitors (serpin), is
transformed into a heat-stabilized form, S-ovalbumin, under elevated pH
conditions. The structural mechanism for the S-ovalbumin formation has long been
a puzzling question in food science and serpin structural biology. On the basis
of the commonly observed serpin thermostabilization by insertion of the reactive
center loop into the proximal beta-sheet, the most widely accepted hypothetical
model has included partial loop insertion. Here we demonstrate, for the first
time, the crystal structure of S-ovalbumin at 1.9-A resolution. This structure
unequivocally excludes the partial loop insertion mechanism; the overall
structure, including the reactive center loop structure, is almost the same as
that of native ovalbumin, except for the significant motion of the preceding
loop of strand 1A away from strand 2A. The most striking finding is that
Ser-164, Ser-236, and Ser-320 take the d-amino acid residue configuration. These
chemical inversions can be directly related to the irreversible and stepwise
nature of the transformation from native ovalbumin to S-ovalbumin. As
conformational changes of the side chains, significant alternations are found in
the values of the chi 1 of Phe-99 and the chi 3 of Met-241. The former
conformational change leads to the decreased solvent accessibility of the
hydrophobic core around Phe-99, which includes Phe-180 and Phe-378, the highly
conserved residues in serpin. This may give a thermodynamic advantage to the
structural stability of S-ovalbumin.
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Figure 2.
FIG. 2. Structural characteristics of S-ovalbumin. a, the
overall main-chain structure of S-ovalbumin. The  -helices
and  -strands are shown in
rose and pink, respectively. b, overall structural differences
between native ovalbumin and S-ovalbumin. S-ovalbumin structure
(pink) is superimposed on native ovalbumin structure (white,
Protein Data Bank accession number 1OVA [PDB]
) in a C^a trace. The reactive center loop assumes almost the
same conformation as that of native ovalbumin. Marked motion of
the preceding loop of strand 1A away from strand 2A (125-128) is
displayed with a red arrow. Three observed configurational
inversions (Ser-164, Ser-236, and Ser-320) and two
conformational transitions (Phe-99 and Met-241) of S-ovalbumin
are shown in ball-and-stick form. The figures were produced with
molecule D using MOL-SCRIPT (48) and Raster3D (49).
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Figure 4.
FIG. 4. Modulation in the hydrophobic interactions around
Phe-99. The side-chain conformation around Phe-99 is shown in
white for native ovalbumin (Protein Data Bank accession number
1OVA [PDB]
) and in pink for S-ovalbumin. The stereo diagram was produced
with molecule D using MOLSCRIPT (48) and Raster3D (49).
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2003,
278,
35524-35530)
copyright 2003.
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