Investigation of interactions between the marine GY785 exopolysaccharide and transforming growth factor-β1 by atomic force microscopy

Sulfated polysaccharides, such as glycosaminoglycans (GAG) regulate various biological activities through their interactions with growth factors. Investigating these interactions becomes the key to understand the structure-function relationship of GAG. Highly sulfated derivatives prepared from the marine GY785 exopolysaccharide (EPS) produced by the deep-sea hydrothermal vent bacterium Alteromonas infernus have previously shown to stimulate the chondrogenic differentiation of mesenchymal stem cells in the presence of Transforming Growth Factor-β1 (TGF-β1). Here, the interactions between the GAG-mimetic GY785 EPS derivatives and TGF-β1 were investigated by Atomic Force Microscopy (AFM). The affinity between slightly sulfated or highly sulfated derivatives and TGF-β1 was explored by AFM imaging and single-molecule force spectroscopy experiments. The number of measured interactions and the interaction strength were both higher for highly sulfated derivative compared to the slightly sulfated one. These results clearly emphasize the involvement of sulfate groups in the protein binding and open new ways to tune cellular processes by designing macromolecules with adjustable sulfate charge density.