Subunit-dependent interaction mechanisms between Lycium barbarum polysaccharides and glutenin: Insights from multi-spectroscopy and molecular dynamics simulations.

Understanding how bioactive polysaccharides modulate the structure and assembly of individual glutenin subunits is important for designing cereal-based protein systems. This study investigated the effects of Lycium barbarum polysaccharides (LBP) on high-molecular-weight glutenin subunits (HMW-GS) and low-molecular-weight glutenin subunits (LMW-GS) using integrated spectroscopic, chromatographic, and molecular dynamics analyses. LBP addition was associated with increased HMW-GS aggregation. At 5% LBP, its free sulfhydryl content decreased from 0.86 to 0.82 μmol/g, while the SDS-insoluble protein fraction increased from 73.00% to 74.52%. In contrast, LMW-GS exhibited reduced secondary-structure order and increased hydrophobic exposure; its β-sheet content decreased from 46.00% to 36.67%, accompanied by an increase in random-coil content from 24.47% to 35.90%. Molecular dynamics analyses provided complementary evidence of distinct protein-LBP interaction patterns, with more extensive and persistent contacts observed for HMW-GS and comparatively localized and dynamic contacts for LMW-GS within the simulated timescale. Importantly, these findings suggest that HMW-GS and LMW-GS undergo distinct structural and assembly responses to the same polysaccharide, challenging the conventional treatment of glutenin as a uniform protein fraction. By identifying glutenin-subunit identity as an important factor influencing polysaccharide-protein interactions, this study provides a subunit-resolved framework for the targeted regulation of gluten structure in cereal-based food systems.