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PDBsum entry 1a0j
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Serine protease
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PDB id
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1a0j
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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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Structure of a non-Psychrophilic trypsin from a cold-Adapted fish species.
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Authors
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H.K.Schrøder,
N.P.Willassen,
A.O.Smalås.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1998,
54,
780-798.
[DOI no: ]
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PubMed id
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Abstract
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The crystal structure of cationic trypsin (CST) from the Atlantic salmon (Salmo
salar) has been refined at 1.70 A resolution. The crystals are orthorhombic,
belong to space group P212121, with lattice parameters a = 65.91, b = 83.11 and
c = 154.79 A, and comprise four molecules per asymmetric unit. The structure was
solved by molecular replacement with AMoRe and refined with X-PLOR to an R value
of 17.4% and Rfree of 21.5% for reflections |F| > 3sigmaF between 8.0 and 1.7 A
resolution. The four non-crystallographic symmetry (NCS) related molecules in
the asymmetric unit display r.m.s. deviations in the range 0.31-0.74 A for
main-chain atoms, with the largest differences confined to two loops. One of
these is the calcium-binding loop where the electron-density indicates a calcium
ion for only one of the four molecules. In order to find structural
rationalizations for the observed difference in thermostability and catalytic
efficiency of CST, anionic salmon trypsin (AST) and bovine trypsin (BT), the
three structures have been extensively compared. The largest deviations for the
superimposed structures occur in the surface loops and particularly in the
so-called 'autolysis loop'. Both the salmon enzymes possess a high methionine
content, lower overall hydrophobicity and enhanced surface hydrophilicity,
compared with BT. These properties have so far been correlated to
cold-adaptation features, while in this work it is shown that the
non-psychrophilic cationic salmon trypsin shares these features with the
psychrophilic anionic salmon trypsin.
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Figure 5.
Fig. 5. Superposition of the C a atoms
of the four independent molecules
in the asymmetric unit. Mol A
(red) and C (green) are shown in
bold lines and Mol B (blue) and D
(orange) in broken lines. The two
most striking differences amng
the four molecules can be seen in
the upper right of the molecules
(residues 37-41 and 69-79). The
three catalytic residues (Aspl02,
His57 and Ser195), benzmidine
inhibitors and the calcium ion are
also included. Every 20th reside
is labelled.
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Figure 9.
Fig. 9. A aA-weighted 2F o - F c map
at 1.3a of the sulfate ion SO4249
of Mol A bound to ArgA156 and
ThrA154, and the neighbouring
ion pair in Mol A: Glual-His 71.
Created by BobScript (Esnouf,
997).
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The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(1998,
54,
780-798)
copyright 1998.
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