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PDBsum entry 1d0d
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Blood clotting inhibitor
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PDB id
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1d0d
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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 tick anticoagulant peptide at 1.6 a resolution complexed with bovine pancreatic trypsin inhibitor.
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Authors
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R.St charles,
K.Padmanabhan,
R.V.Arni,
K.P.Padmanabhan,
A.Tulinsky.
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Ref.
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Protein Sci, 2000,
9,
265-272.
[DOI no: ]
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PubMed id
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Abstract
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The structure of tick anticoagulant peptide (TAP) has been determined by X-ray
crystallography at 1.6 A resolution complexed with bovine pancreatic trypsin
inhibitor (BPTI). The TAP-BPTI crystals are tetragonal, a = b = 46.87, c = 50.35
A, space group P41, four complexes per unit cell. The TAP molecules are highly
dipolar and form an intermolecular helical array along the c-axis with a
diameter of about 45 A. Individual TAP units interact in a head-to-tail fashion,
the positive end of one molecule associating with the distal negative end of
another, and vice versa. The BPTI molecules have a uniformly distributed
positively charged surface that interacts extensively through 14 hydrogen bonds
and two hydrogen bonded salt bridges with the helical groove around the helical
TAP chains. Comparing the structure of TAP in TAP-BPTI with TAP bound to factor
Xa(Xa) suggests a massive reorganization in the N-terminal tetrapeptide and the
first disulfide loop of TAP (Cys5T-Cys15T) upon binding to Xa. The Tyr1(T)OH
atom of TAP moves 14.2 A to interact with Asp189 of the S1 specificity site,
Arg3(T)CZ moves 5.0 A with the guanidinium group forming a cation-pi-electron
complex in the S4 subsite of Xa, while Lys7(T)NZ differs in position by 10.6 A
in TAP-BPTI and TAP-Xa, all of which indicates a different pre-Xa-bound
conformation for the N-terminal of TAP in its native state. In contrast to TAP,
the BPTI structure of TAP-BPTI is practically the same as all those of
previously determined structures of BPTI, only arginine and lysine side-chain
conformations showing significant differences.
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