1plf
From Proteopedia
|
THE THREE-DIMENSIONAL STRUCTURE OF BOVINE PLATELET FACTOR 4 AT 3.0 ANGSTROMS RESOLUTION
Overview
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.
About this Structure
1PLF is a Single protein structure of sequence from Bos taurus with TCN as ligand. Full crystallographic information is available from OCA.
Reference
The three-dimensional structure of bovine platelet factor 4 at 3.0-A resolution., St Charles R, Walz DA, Edwards BF, J Biol Chem. 1989 Feb 5;264(4):2092-9. PMID:2914894
Page seeded by OCA on Tue Nov 20 23:54:37 2007
