The three-dimensional Structure of Bovine Platelet Factor 4 at 3.0-A Resolution

Charles, R. St; Walz, Daniel A.; Edwards, Brian F.P.

doi:10.1016/s0021-9258(18)94146-3

Cited by 175 publications

(13 citation statements)

References 57 publications

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“…Separation of PF4 from its proteoglycan counterpart gave rise to a protein that could be readily dis-solved at an acidic pH but remained insoluble under physiological conditions (27). All subsequent structural work with PF4 (e.g., x-ray crystallography studies) was carried out either under mildly acidic conditions or at an ionic strength that significantly exceeded the physiologically relevant levels (7,8). Elevation of the ionic strength of the PF4 solution gave rise to a progressively increasing ionic signal for the tetrameric form of this protein, although even at the highest ionic strength examined in these measurements (1.5 M), a prominent signal of the monomeric form of PF4 was still detected (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Despite PF4-heparin association being an important aspect in the etiology of HIT, relatively little is known about the specific molecular mechanism of this interaction. Even before the crystal structures of PF4 (showing the continuous ring of positive potential encircling the PF4 tetramer (7,8)) became available, suggestions were made that the heparin chain wraps around the tetramer to maximize electrostatic contacts (mostly with the lysine-rich C-termini of the constituent polypeptide chains) (9), a conjecture that was mostly confirmed by modeling the interaction using the coordinates of PF4 tetrameric structure (10). Later NMR studies expanded the repertoire of heparin-binding sites within PF4 to include several arginine, lysine, and histidine residues located outside of the C-terminal helix (11) and provided evidence that heparin may play an important role in fine-tuning the protein conformation and indeed control both PF4 folding and assembly of its quaternary structure (12).…”

Section: Introductionmentioning

confidence: 99%

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Platelet Factor 4 Interactions with Short Heparin Oligomers: Implications for Folding and Assembly

Niu

Yang

Huynh

et al. 2020

Biophysical Journal

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Association of platelet factor 4 (PF4) with heparin is a first step in formation of aggregates implicated in the development of heparin-induced thrombocytopenia (HIT), a potentially fatal immune disorder affecting 1-5% of patients receiving heparin. Despite being a critically important element in HIT etiology, relatively little is known about the specific molecular mechanism of PF4-heparin interactions. This work uses native mass spectrometry to investigate PF4 interactions with relatively short heparin chains (up to decasaccharides). The protein is shown to be remarkably unstable at physiological ionic strength in the absence of polyanions; only monomeric species are observed, and the extent of multiple charging of corresponding ions indicates a partial loss of conformational integrity. The tetramer signal remains at or below the detection threshold in the mass spectra until the solution's ionic strength is elevated well above the physiological level, highlighting the destabilizing role played by electrostatic interactions vis-à -vis quaternary structure of this high-pI protein. The tetramer assembly is dramatically facilitated by relatively short polyanions (synthetic heparin-mimetic pentasaccharide), with the majority of the protein molecules existing in the tetrameric state even at physiological ionic strength. Each tetramer accommodates up to six pentasaccharides, with at least three such ligands required to guarantee the higher-order structure integrity. Similar results are obtained for PF4 association with longer and structurally heterogeneous heparin oligomers (decamers). These longer polyanions can also induce PF4 dimer assembly when bound to the protein in relatively low numbers, lending support to a model of PF4/heparin interaction in which the latter wraps around the protein, making contacts with multiple subunits. Taken together, these results provide a more nuanced picture of PF4-glycosaminoglycan interactions leading to complex formation. This work also advocates for a greater utilization of native mass spectrometry in elucidating molecular mechanisms underlying HIT, as well as other physiological processes driven by electrostatic interactions.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Platelet Factor 4 Interactions with Short Heparin Oligomers: Implications for Folding and Assembly

Niu

Yang

Huynh

et al. 2020

Biophysical Journal

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“…It was recently reported that introduction of three carboxy-terminal mutations into MIP-la rendered it monomeric at concentrations where wild-type MIPla is highly self-associated, yet there was no change in biological activity (Graham et al, 1994). Furthermore, the monomer conformation of self-associated forms of chemokines appears to be conserved for IL-8, PF4, and MIP-1 ß (Baldwin et al, 1991;Charles et al, 1989;Clore et al, 1990;Lodi et al, 1994), despite differences in the way that IL-8 and PF4 associate compared to MIP-ljS.…”

Section: Discussionmentioning

confidence: 99%

“…IL-8 is secreted predominantly as an 8-kDa, 72 amino acid species with two internal disulfide bridges (Baggiolini & Clark-Lewis, 1992;Oppenheim et al, 1991). NMR and X-ray crystallography show that IL-8 is a homodimer (Baldwin et al, 1991;Clore et al, 1990) and reveal a structure related to platelet factor-4, another member of the chemokine family, which is tetrameric (Charles et al, 1989). Other members of the chemokine family, such as MIP-ljS (Lodi et al, 1994), are also structurally similar and tend to self-associate (Graham et al, 1994).…”

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confidence: 99%

Determination of the monomer-dimer equilibrium of interleukin-8 reveals it is a monomer at physiological concentrations

Burrows¹,

Doyle²,

Murphy³

et al. 1994

Biochemistry

155

124

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Interleukin-8 has been shown by X-ray crystallography and NMR to be a homodimer, suggesting that this is the form which binds to its receptor. Here we measure, for the first time, the monomer-dimer equilibrium of interleukin-8 using analytical ultracentrifugation and titration microcalorimetry and find that it dissociates readily to monomers with an equilibrium dissociation constant of 18 +/- 6 microM at 37 degrees C. The present findings suggest that the monomer is the form which binds to the receptor. Comparison of experimental and structure-based calculated thermodynamics of interleukin-8 dimerization argues for limited subunit conformational changes upon dissociation to monomer.

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“…To understand the complex interplay between chemokines and their receptors on a structural basis, several three-dimensional chemokine structures have been determined by either NMR spectroscopy or X-ray crystallography: PF-4 ( , ), IL-8 ( , ), MGSA ( − ), Chi1 (), CINC/Gro ( , ), NAP-2 (), MIP-2 (), SDF-1α (), MIP-1β (), RANTES ( , ), MCP-1 ( , ), MCP-3 ( , ), and Eotaxin (). In all cases, the monomeric subunit exhibits a quite similar secondary and tertiary structure consisting of a triple-stranded antiparallel β-sheet packed against a carboxy-terminal α-helix, while the quaternary contacts of these proteins vary strongly.…”

mentioning

confidence: 99%

Solution Structure of the Human CC Chemokine 2: A Monomeric Representative of the CC Chemokine Subtype^,

et al. 1999

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HCC-2, a 66-amino acid residue human CC chemokine, was reported to induce chemotaxis on monocytes, T-lymphocytes, and eosinophils. The three-dimensional structure of HCC-2 has been determined by 1 H nuclear magnetic resonance (NMR) spectroscopy and restrained molecular dynamics calculations on the basis of 871 experimental restraints. The structure is well-defined, exhibiting average root-mean-square deviations of 0.58 and 0.96 Å for the backbone heavy atoms and all heavy atoms of residues 5-63, respectively. In contrast to most other chemokines, subtle structural differences impede dimer formation of HCC-2 in a concentration range of 0.1 µM to 2 mM. HCC-2, however, exhibits the same structural elements as the other chemokines, i.e., a triple-stranded antiparallel -sheet covered by an R-helix, showing that the chemokine fold is not influenced by quaternary interactions. Structural investigations with a HCC-2 mutant prove that a third additional disulfide bond present in wild-type HCC-2 is not necessary for maintaining the relative orientation of the helix and the -sheet.

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The three-dimensional Structure of Bovine Platelet Factor 4 at 3.0-A Resolution

Cited by 175 publications

References 57 publications

Platelet Factor 4 Interactions with Short Heparin Oligomers: Implications for Folding and Assembly

Platelet Factor 4 Interactions with Short Heparin Oligomers: Implications for Folding and Assembly

Determination of the monomer-dimer equilibrium of interleukin-8 reveals it is a monomer at physiological concentrations

Solution Structure of the Human CC Chemokine 2: A Monomeric Representative of the CC Chemokine Subtype^,

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The three-dimensional Structure of Bovine Platelet Factor 4 at 3.0-A Resolution

Cited by 175 publications

References 57 publications

Platelet Factor 4 Interactions with Short Heparin Oligomers: Implications for Folding and Assembly

Platelet Factor 4 Interactions with Short Heparin Oligomers: Implications for Folding and Assembly

Determination of the monomer-dimer equilibrium of interleukin-8 reveals it is a monomer at physiological concentrations

Solution Structure of the Human CC Chemokine 2: A Monomeric Representative of the CC Chemokine Subtype,

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Solution Structure of the Human CC Chemokine 2: A Monomeric Representative of the CC Chemokine Subtype^,