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PDBsum entry 1bpi
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Proteinase inhibitor (trypsin)
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PDB id
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1bpi
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References listed in PDB file
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Key reference
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Title
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Structure of bovine pancreatic trypsin inhibitor at 125 k definition of carboxyl-Terminal residues gly57 and ala58.
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Authors
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S.Parkin,
B.Rupp,
H.Hope.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1996,
52,
18-29.
[DOI no: ]
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PubMed id
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Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
percentage match of
85%.
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Abstract
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The structure of bovine pancreatic trypsin inhibitor has been refined to a
resolution of 1.1 A against data collected at 125 K. The space group of the form
II crystal is P2(1)2(1)2(1) with a = 75.39(3), b = 22.581(7), c = 28.606 (9) A
(cf. a = 74.1, b = 23.4, c = 28.9 A at room temperature). The structure was
refined by restrained least-squares minimization of summation operator w(F
(o)(2)- F (c)(2))(2) with the SHELXL93 program. As the model improved, water
molecules were included and exceptionally clear electron density was found for
two residues, Gly57 and Ala58, that had been largely obscured at room
temperature. The side chains of residues Glu7 and Arg53 were modelled over two
positions with refined occupancy factors. The final model contains 145.6 water
molecules distributed over 167 sites, and a single phosphate group disordered
over two sites. The root-mean-square discrepancy between Calpha atoms in
residues Arg1-Gly56 at room and low temperatures is 0.4 A. A comparison of
models refined with anisotropic and isotropic thermal parameters revealed that
there were no significant differences in atomic positions. The final weighted
R-factor on F(2) (wR(2)) for data in the range 10-1.1 A was 35.9% for the
anisotropic model and 40.9% for the isotropic model. Conventional R-factors
based on F for F > 4sigma(F) were 12.2 and 14.6%, respectively, corresponding
to 16.1 and 18.7% on all data. These large R-factor differences were not
reflected in values of R(free), which were not significantly different at
21.5(5) and 21.8(4)%, respectively. These results, along with the relatively
straightforward nature of the refinement, clearly highlight the benefits of
low-temperature data collection.
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Figure 4.
Fig. 4. Electron densities contoured at i.0~ and 0.5a (coefficients
Fobs)
at the tw residues (a) Glu7 and (b) Arg53 for which refined
disorder models were included.
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Figure 7.
Fig. 7. Electron densities contoured at la, 3a and 5a (coefficients Fobs.) in regions with high refined thermal parameters at 125 K, the side chains of
residues (a) Asp3, (b) Lysl5, (c) Arg39 and (d) Arg42.
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The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(1996,
52,
18-29)
copyright 1996.
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