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PDBsum entry 1an1
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Complex (serine protease/inhibitor)
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PDB id
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1an1
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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 the complex of leech-Derived tryptase inhibitor (ldti) with trypsin and modeling of the ldti-Tryptase system.
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Authors
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S.Di marco,
J.P.Priestle.
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Ref.
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Structure, 1997,
5,
1465-1474.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Tryptase is a trypsin-like serine proteinase stored in the
cytoplasmic granules of mast cells, which has been implicated in a number of
mast cell related disorders such as asthma and rheumatoid arthritis. Unlike
almost all other serine proteinases, tryptase is fully active in plasma and in
the extracellular space, as there are no known natural inhibitors of tryptase in
humans. Leech-derived tryptase inhibitor (LDTI), a protein of 46 amino acids, is
the first molecule found to bind tightly to and specifically inhibit human
tryptase in the nanomolar range. LDTI also inhibits trypsin and chymotrypsin
with similar affinities. The structure of LDTI in complex with an inhibited
proteinase could be used as a template for the development of low molecular
weight tryptase inhibitors. RESULTS: The crystal structure of the complex
between trypsin and LDTI was solved at 2.0 A resolution and a model of the
LDTI-tryptase complex was created, based on this X-ray structure. LDTI has a
very similar fold to the third domain of the turkey ovomucoid inhibitor. LDTI
interacts with trypsin almost exclusively through its binding loop (residues
3-10) and especially through the sidechain of the specificity residue Lys8. Our
modeling studies indicate that these interactions are maintained in the
LDTI-tryptase complex. CONCLUSIONS: The insertion of nine residues after residue
174 in tryptase, relative to trypsin and chymotrypsin, prevents inhibition by
other trypsin inhibitors and is certainly responsible for the higher specificity
of tryptase relative to trypsin. In LDTI, the disulfide bond between residues 4
and 25 causes a sharp turn from the binding loop towards the N terminus, holding
the N terminus away from the 174 loop of tryptase.
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Figure 6.
Figure 6. Electrostatic potential surface representation of
the model of tryptase. (a) The region around the active site,
including the binding loop of LDTI. (b) The same view as (a) but
rotated 180°. The sidechains of the specificity residues P4 to
P3' of LDTI are labeled (nomenclature of Berger and Schechter
[26]), although Ala5 (P4) is hidden under the tryptase 174
insertion loop and Lys8 (P1) is buried in the S1 specificity
pocket. The highly electronegative active-site area (red)
corresponds well to the positively charged LDTI molecule (pI >
10). The concentrated positively charged region (blue) in
tryptase, shown at the bottom of (b), could be responsible for
heparin binding. (The figure was made with the program GRASP
[43].)
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The above figure is
reprinted
by permission from Cell Press:
Structure
(1997,
5,
1465-1474)
copyright 1997.
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Secondary reference #1
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Title
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Purification, Characterization and biological evaluation of recombinant leech-Derived tryptase inhibitor (rldti) expressed at high level in the yeast saccharomyces cerevisiae.
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Authors
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G.Pohlig,
G.Fendrich,
R.Knecht,
B.Eder,
G.Piechottka,
C.P.Sommerhoff,
J.Heim.
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Ref.
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Eur J Biochem, 1996,
241,
619-626.
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PubMed id
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Secondary reference #2
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Title
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A kazal-Type inhibitor of human mast cell tryptase: isolation from the medical leech hirudo medicinalis, Characterization, And sequence analysis.
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Authors
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C.P.Sommerhoff,
C.Söllner,
R.Mentele,
G.P.Piechottka,
E.A.Auerswald,
H.Fritz.
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Ref.
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Biol Chem Hoppe Seyler, 1994,
375,
685-694.
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PubMed id
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