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PDBsum entry 1plf
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Platelet factor
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PDB id
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1plf
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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 three-Dimensional structure of bovine platelet factor 4 at 3.0-A resolution.
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Authors
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R.St charles,
D.A.Walz,
B.F.Edwards.
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Ref.
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J Biol Chem, 1989,
264,
2092-2099.
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PubMed id
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Abstract
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Platelet factor 4 (PF4), which is released by platelets during coagulation,
binds very tightly to negatively charged oligosaccharides such as heparin. To
date, six other proteins are known that are homologous in sequence with PF4 but
have quite different functions. The structure of a tetramer of bovine PF4
complexed with one Ni(CN)4(2-) molecule has been determined at 3.0 A resolution
and refined to an R factor of 0.28. The current model contains residues 24-85,
no solvent, and one overall temperature factor. Residues 1-13, which carried an
oligosaccharide chain, were removed with elastase to induce crystallization;
residues 14-23 and presumably 86-88 are disordered in the electron density map.
Because no heavy atom derivative was isomorphous with the native crystals, the
complex of PF4 with one Ni(CN)4(2-) molecule was solved using a single, highly
isomorphous Pt(CN)4(2-) derivative and the iterative, single isomorphous
replacement method. The secondary structure of the PF4 subunit, from amino- to
carboxyl-terminal end, consists of an extended loop, three strands of
antiparallel beta-sheet arranged in a Greek key, and one alpha-helix. The
tetramer contains two extended, six-stranded beta-sheets, each formed by two
subunits, which are arranged back-to-back to form a "beta-bilayer" structure
with two buried salt bridges sandwiched in the middle. The carboxyl-terminal
alpha-helices, which contain lysine residues that are thought to be intimately
involved in binding heparin, are arranged as antiparallel pairs on the surface
of each extended beta-sheet.
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Secondary reference #1
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Title
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X-Ray diffraction analysis of crystals of bovine platelet factor 4.
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Authors
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R.St charles,
R.E.Ciaglowski,
D.Walz,
B.F.Edwards.
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Ref.
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J Mol Biol, 1984,
176,
421-423.
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PubMed id
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