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PDBsum entry 1g0v
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Hydrolase/hydrolase inhibitor
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PDB id
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1g0v
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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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The potency and specificity of the interaction between the ia3 inhibitor and its target aspartic proteinase from saccharomyces cerevisiae.
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Authors
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L.H.Phylip,
W.E.Lees,
B.G.Brownsey,
D.Bur,
B.M.Dunn,
J.R.Winther,
A.Gustchina,
M.Li,
T.Copeland,
A.Wlodawer,
J.Kay.
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Ref.
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J Biol Chem, 2001,
276,
2023-2030.
[DOI no: ]
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PubMed id
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Abstract
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The yeast IA3 polypeptide consists of only 68 residues, and the free inhibitor
has little intrinsic secondary structure. IA3 showed subnanomolar potency toward
its target, proteinase A from Saccharomyces cerevisiae, and did not inhibit any
of a large number of aspartic proteinases with similar sequences/structures from
a wide variety of other species. Systematic truncation and mutagenesis of the
IA3 polypeptide revealed that the inhibitory activity is located in the
N-terminal half of the sequence. Crystal structures of different forms of IA3
complexed with proteinase A showed that residues in the N-terminal half of the
IA3 sequence became ordered and formed an almost perfect alpha-helix in the
active site of the enzyme. This potent, specific interaction was directed
primarily by hydrophobic interactions made by three key features in the
inhibitory sequence. Whereas IA3 was cut as a substrate by the nontarget
aspartic proteinases, it was not cleaved by proteinase A. The random coil IA3
polypeptide escapes cleavage by being stabilized in a helical conformation upon
interaction with the active site of proteinase A. This results, paradoxically,
in potent selective inhibition of the target enzyme.
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Figure 2.
Fig. 2. Stereo representation of the interactions made by
the side chains of Val8 and Phe^12 in the IA[3] polypeptide with
cognate hydrophobic residues in proteinase A. Proteinase A
residues are green while the Val8 and Phe^12 side chains and the
appropriate segment of the IA[3] helical backbone are in brown.
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Figure 3.
Fig. 3. Stereo representation of the interactions made by
the ~Lys18-Leu19-X-X-Asp22~ centerpiece residues of IA[3] in the
vicinity of the active site of proteinase A. Proteinase A
residues are in green with the catalytic water molecule depicted
as a blue sphere. The side chains of Lys18, Leu19, and Asp22
plus the relevant segment of the IA[3] helix backbone are in
brown. Hydrogen bonding distances are shown.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2001,
276,
2023-2030)
copyright 2001.
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Secondary reference #1
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Title
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The aspartic proteinase from saccharomyces cerevisiae folds its own inhibitor into a helix.
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Authors
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M.Li,
L.H.Phylip,
W.E.Lees,
J.R.Winther,
B.M.Dunn,
A.Wlodawer,
J.Kay,
A.Gustchina.
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Ref.
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Nat Struct Biol, 2000,
7,
113-117.
[DOI no: ]
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PubMed id
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Figure 1.
Figure 1. Schematic diagram of the structure of proteinase A.
Ribbon representation showing the tracing of the main chain of
proteinase A (green) with the oligosaccharide attached to Asn 67
shown in mauve, together with the visible fragment of the
inhibitor IA[3] (gold). Side chains of the active site residues
Asp 32 and Asp 215 are shown in red.
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Figure 3.
Figure 3. Interactions in the vicinity of the active site of
proteinase A. Proteinase A (green, with the active site
aspartates red) complexed to IA[3] (yellow with orange side
chains) is superimposed on progastricsin (purple). Water
molecules in the proteinase A complex are blue, and hydrogen
bonds are marked as thin lines.
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The above figures are
reproduced from the cited reference
with permission from Macmillan Publishers Ltd
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