Dataset Information

Electrostatic Forces as Dominant Interactions Between Proteins and Polyanions: an ESI MS Study of Fibroblast Growth Factor Binding to Heparin Oligomers.

ABSTRACT: The interactions between fibroblast growth factors (FGFs) and their receptors (FGFRs) are facilitated by heparan sulfate (HS) and heparin (Hp), highly sulfated biological polyelectrolytes. The molecular basis of FGF interactions with these polyelectrolytes is highly complex due to the structural heterogeneity of HS/Hp, and many details still remain elusive, especially the significance of charge density and minimal chain length of HS/Hp in growth factor recognition and multimerization. In this work, we use electrospray ionization mass spectrometry (ESI MS) to investigate the association of relatively homogeneous oligoheparins (octamer, dp8, and decamer, dp10) with acidic fibroblast growth factor (FGF-1). This growth factor forms 1:1, 2:1, and 3:1 protein/heparinoid complexes with both dp8 and dp10, and the fraction of bound protein is highly dependent on protein/heparinoid molar ratio. Multimeric complexes are preferentially formed on the highly sulfated Hp oligomers. Although a variety of oligomers appear to be binding-competent, there is a strong correlation between the affinity and the overall level of sulfation (the highest charge density polyanions binding FGF most strongly via multivalent interactions). These results show that the interactions between FGF-1 and Hp oligomers are primarily directed by electrostatics, and also demonstrate the power of ESI MS as a tool to study multiple binding equilibria between proteins and structurally heterogeneous polyanions. Graphical Abstract ?.

SUBMITTER: Minsky BB

PROVIDER: S-EPMC5808462 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Electrostatic Forces as Dominant Interactions Between Proteins and Polyanions: an ESI MS Study of Fibroblast Growth Factor Binding to Heparin Oligomers.

Minsky Burcu Baykal BB Dubin Paul L PL Kaltashov Igor A IA

Journal of the American Society for Mass Spectrometry 20170216 4

The interactions between fibroblast growth factors (FGFs) and their receptors (FGFRs) are facilitated by heparan sulfate (HS) and heparin (Hp), highly sulfated biological polyelectrolytes. The molecular basis of FGF interactions with these polyelectrolytes is highly complex due to the structural heterogeneity of HS/Hp, and many details still remain elusive, especially the significance of charge density and minimal chain length of HS/Hp in growth factor recognition and multimerization. In this wo ...[more]

PMID: 28211013

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Project description: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.

Dataset Information

Electrostatic Forces as Dominant Interactions Between Proteins and Polyanions: an ESI MS Study of Fibroblast Growth Factor Binding to Heparin Oligomers.

Publications

Electrostatic Forces as Dominant Interactions Between Proteins and Polyanions: an ESI MS Study of Fibroblast Growth Factor Binding to Heparin Oligomers.

Similar Datasets

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