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Heparin binding to monodisperse plasma fibronectin induces aggregation without large-scale changes in conformation in
L Vuillard1, D J Hulmes, I F Purdom
1Department of Biochemistry, University of Edinburgh, UK.
International Journal of Biological Macromolecules
|February 1, 1994
Summary
This study shows that heparin binding to fibronectin monomers does not cause significant conformational changes. Minimizing polydispersity is crucial for accurate biophysical analysis of fibronectin in solution.
Area of Science:
- Biochemistry
- Biophysics
- Protein Chemistry
Background:
- Plasma fibronectin is a key extracellular matrix protein involved in cell adhesion and wound healing.
- Understanding fibronectin's behavior in solution is critical for its therapeutic applications.
- Previous studies have not fully elucidated the conformational changes upon heparin binding.
Purpose of the Study:
- To investigate the conformational changes of plasma fibronectin upon heparin binding.
- To assess the impact of polydispersity on fibronectin's biophysical properties.
- To determine the binding interactions between fibronectin and heparin.
Main Methods:
- Purification of plasma fibronectin using gelatin affinity chromatography.
- Minimizing polydispersity via gel permeation fast protein liquid chromatography (FPLC) on Superose 6.
- Analysis of translational diffusion coefficient (D20,w) and polydispersity using photon correlation spectroscopy.
- Studying fibronectin aggregation induced by heparin using static light scattering.
- Circular dichroism spectroscopy to assess conformational changes.
- Fluorescence polarization to quantify heparin binding site occupancy.
Main Results:
- FPLC successfully separated fibronectin monomers from aggregates, reducing polydispersity.
- Heparin addition induced fibronectin aggregation, increasing light scattering intensity and polydispersity.
- Monomeric fibronectin's translational diffusion coefficient remained unaffected by heparin binding, even at high binding site occupancy.
- Small circular dichroism spectral differences were observed upon aggregate removal and heparin addition.
Conclusions:
- Minimizing polydispersity is essential for reliable biophysical characterization of fibronectin.
- Heparin binding to monomeric fibronectin occurs without significant large-scale conformational alterations.
- Aggregated forms of fibronectin may exhibit more extended conformations upon heparin binding.