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PDBsum entry 1pbi
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Bowman-birk inhibitor
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PDB id
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1pbi
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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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Dimeric crystal structure of a bowman-Birk protease inhibitor from pea seeds.
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Authors
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I.Li de la sierra,
L.Quillien,
P.Flecker,
J.Gueguen,
S.Brunie.
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Ref.
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J Mol Biol, 1999,
285,
1195-1207.
[DOI no: ]
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PubMed id
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Abstract
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The trypsin/chymotrypsin inhibitors from winter pea seeds (PsTI) are members of
the Bowman-Birk protease inhibitor (BBPI) family. The crystal structure of the
isoform PsTI-IVb was determined by molecular replacement at 2.7 A resolution
using the X-ray co-ordinates of the soybean inhibitor as a search model. The
inhibitor crystallized with a nearly perfect 2-fold symmetric dimer in the
asymmetric unit. Although the overall structure is very similar to that seen in
other BBPIs, there are notable new structural features. Unlike the previously
reported X-ray structures of BBPIs, the structure of PsTI-IVb includes the
C-terminal segment of the molecule. The C-terminal tail of each subunit is
partly beta-stranded and interacts with the 2-fold symmetry-related subunit,
forming a beta-sheet with strands A and B of this subunit. The dimer is mainly
stabilized by a large internal hydrogen-bonded network surrounded by two
hydrophobic links. Fluorescence anisotropy decay measurements show that residues
Tyr59 and Tyr43 are mobile in the picosecond time scale with a large amplitude.
The fluorescence study and a molecular model of the simultaneous binding of
PsTI-IVb to porcine trypsin and bovine chymotrypsin are compatible only with a
monomeric state of the functional molecule in solution.
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Figure 3.
Figure 3. Hydrogen bond network of the interfacial
domain of the dimer. Only relevant residues are shown
in white for one subunit and black for the second sub-
unit.
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Figure 5.
Figure 5. (a) Molecular model of the PsTI/trypsin/chymotrypsin ternary complex showing the independent and
non-interacting trypsin and chymotrypsin sites. This model is consistent with simultaneous binding of the two pro-
teases. The PsTI molecule is shown in a green ribbon diagram, the molecular surfaces (calculated with the pro-
gramme GRASP) of trypsin and chymotrypsin are in yellow and blue, respectively. (b) Main interactions between
PsTI and trypsin. Hydrogen bonds are represented with broken lines. PsTI is in black and trypsin in white. (c) View
showing the complementarity between the phenyl ring of Tyr43 and the S1 pocket of chymotrypsin. The alpha-car-
bon trace of PsTI as well as all atoms of residue Tyr43, are shown in green. Residues of chymotrypsin which under-
line the pocket are in light blue. The S1 pocket of chymotrypsin is represented as a transparent surface. This
illustration was prepared using the programmes MOLSCRIPT, GRASP and RASTER3D (Merritt & Murphy, 1994).
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1999,
285,
1195-1207)
copyright 1999.
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