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PDBsum entry 1dlk
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Hydrolase/hydrolase inhibitor
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PDB id
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1dlk
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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 delta-Chymotrypsin bound to a peptidyl chloromethyl ketone inhibitor.
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Authors
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A.Mac sweeney,
G.Birrane,
M.A.Walsh,
T.O'Connell,
J.P.Malthouse,
T.M.Higgins.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2000,
56,
280-286.
[DOI no: ]
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PubMed id
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Abstract
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Chymotrypsin is a member of the trypsin family of serine proteases and is one of
the first proteins successfully studied by X-ray crystallography. It is secreted
into the intestine as the inactive precursor chymotrypsinogen; four sequential
cleavages of the peptide bonds following residues 13, 15, 146 and 148 occur to
generate the active pi, delta, kappa and alpha forms of chymotrypsin. (13)C NMR
that when
the delta form of chymotrypsin is inhibited by 2-(13)C-enriched
benzyloxycarbonylglycylglycylphenylalanyl chloromethane, a tetrahedral adduct is
formed which is thought to be analogous to the tetrahedral intermediate formed
during catalysis. This inhibitor complex has been crystallized as a dimer in
space group P4(1)2(1)2. The structure has been refined at 2.14 A resolution to
an R value of 21.2% (free R = 25.2%). Conformational differences between
delta-chymotrypsin and chymotrypsinogen in the region of the flexible autolysis
loop (residues 145-150) were observed. This is the first crystal structure of
delta-chymotrypsin and includes two residues which are disordered in previous
crystal structures of active chymotrypsin. A difference of 11.3 A(2) between the
average B values of the monomers within the asymmetric unit is caused by
lattice-disordering effects approximating to rotation of the molecules about a
crystallographic screw axis. The substrate-binding mode of the inhibitor was
similar to other chymotrypsin peptidyl inhibitor complexes, but this is the
first published chymotrypsin structure in which the tetrahedral chloromethyl
ketone transition-state analogue is observed. This structure is compared with
that of a similar tetrahedral transition-state analogue which does not alkylate
the active-site histidine residue.
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Figure 1.
Figure 1 Activation scheme of chymotrypsinogen.
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Figure 5.
Figure 5 A comparison of the structures of the tetrahedral
adducts formed when chymotrypsin is inhibited by (a)
Z-Gly-Gly-(2-13C)Phe-CH[2]Cl and (b) Z-Leu-Phe-CF[3].
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The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(2000,
56,
280-286)
copyright 2000.
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