Stoichiometry of heparin binding to basic fibroblast growth factor

Area of Science:

• Biochemistry
• Molecular Biology
• Protein-Carbohydrate Interactions

Background:

• Fibroblast growth factors (FGFs) are crucial for cell growth and development.
• FGFs exhibit strong binding affinity for heparin, which stabilizes them.
• Understanding FGF-heparin interactions is key to their biological function and therapeutic potential.

Purpose of the Study:

• To investigate the binding stoichiometry of basic fibroblast growth factor (bFGF) to heparin.
• To determine the number of bFGF molecules that can bind to low- and high-molecular-weight heparin.
• To characterize the heparin binding sites for bFGF.

Main Methods:

• Size exclusion chromatography coupled with light scattering, absorbance, and refractive index detection.
• Preparation of mixtures with varying ratios of bFGF to low-molecular-weight heparin (LMWH) and high-molecular-weight heparin (HMWH).
• Analysis of eluted complexes to determine molecular weight and composition.

Main Results:

• bFGF forms stable complexes with both LMWH and HMWH.
• LMWH binds an average of 2.5 bFGF molecules per heparin molecule, indicating heterogeneity in binding.
• HMWH binds approximately 6-7 bFGF molecules per heparin molecule.
• Both heparin types provide approximately 2300 Da per bFGF binding site, corresponding to an octasaccharide.

Conclusions:

• Heparin acts as a scaffold for bFGF, enabling close packing of protein molecules.
• The binding stoichiometry suggests specific interaction sites on heparin for bFGF.
• These findings provide insights into the structural basis of FGF-heparin interactions.