Fructooligosaccharides binding property of the LPxTG-motif surface protein derived from <em>Limosilactobacillus reuteri</em>

As one of the adhesion-related surface factors on the cell wall of <em>Lactobacillus</em> strains, Leu-Pro-x-Thr-Gly (LPxTG) motif anchored proteins play a critical role in adhesion and molecular cross-talk with the host in the gastrointestinal tract (GIT). This study allows to understand that the combination of LPxTG anchoring proteins (LMP) and fructooligosaccharides (FOS) can have a better promoting effect on lactic acid bacteria. In this study, molecular docking and molecular dynamics simulations were employed to investigate the interaction properties of LMP from <em>L. reuteri</em> SH23 with small nutrient molecules in the host gastrointestinal tract. The thermodynamic parameters ΔG⁰, ΔH⁰, and ΔS⁰ were calculated as -4.850 kJ/mol, -219.071 kJ/mol, and -718.501 J/mol-K, respectively, for a binding constant of 1.414 × 10⁴ μL/mol at 298.15 K. Fluorescence spectroscopy (FL) and circular dichroism spectroscopy (CD) were also utilised to study the interaction of LMP with the small nutrient molecules. It was found that LMP interacts with the small nutrient molecule FOS primarily through van der Waals and electrostatic forces. The transition from β-folding and random coiling to α-helix and β-sheet also indicates structural changes in the protein during the binding process. Furthermore, the binding of LMP to FOS not only improved the adhesion of the strain to intestinal epithelial cells and increased the auto-aggregation of the strain, but also promoted the growth of <em>L. reuteri</em> SH23. These findings provide a better understanding of Lactobacillus and host interactions at the cell surface protein level.