Interaction of Escherichia coli heat-labile enterotoxin B-pentamer with exopolysaccharides from Leuconostoc mesenteroides P35: Insights from surface plasmon resonance and molecular docking studies

In this study, the interaction of exopolysaccharides from Leuconostoc mesenteroides P35 (EPS-LM) with Escherichia coli heat-labile enterotoxin B-pentamer (LTB) was investigated at different concentrations and temperatures by using surface plasmon resonance (SPR) and molecular docking approaches. FT-IR spectral analysis together with HPTLC analysis revealing that glucose is the only constitutive monosaccharide of EPS-LM suggests that its structure is composed of dextran with alpha-D (1 -> 6) glycosidic linkages. SPR analysis revealed the high affinity of EPS-LM for immobilized LTB toxin (KA=(2.05 +/- 0.04) x 106 mol.L-1 at 37 degrees C). The binding process was spon-taneous (Delta G<0), endothermic (Delta H>0), and entropy-driven (Delta S>0) with an increase of KA with temperature. This suggests that EPS-LM -LTB interaction is dominated by hydrophobic forces. The binding affinity of EPS-LM to LTB had negligible dependence on enthalpy (Delta H = 0.084 kJ mol-1). Further, molecular docking results suggested the presence of some binding sites of EPS-LM on the LTB through hydrophobic forces (Lys, Asp, Arg, Glu) and also hydrogen bonding (Glu) in the hydrophobic core of LTB. Besides autodock studies, Schiffer-Edmundson helical wheel diagrams of LTB in alpha-helix domain suggested that LTB hydrophobic core is a highly effective region, which was able to form favorable non-polar interactions of the protein's binding surface (with amino acids residues such as Tyr, Leu, Ile) with EPS-LM. This study provided thus further insights into the in-teractions between EPS-LM and LTB, suggesting that EPS produced by some LAB, such as EPS produced by Ln. mesenteroides P35 strain are good candidates to inhibit E. coli toxin activity.

Automated summary

In this study, the interaction between exopolysaccharides from Leuconostoc mesenteroides P35 and Escherichia coli heat-labile enterotoxin B-pentamer was investigated. The results showed that the binding process was driven by hydrophobic forces and EPS-LM had a high affinity for LTB.