Interaction of γ-conglutin from Lupinus albus with model phospholipid membranes: Investigations on structure, thermal stability and oligomerization status.

Abstract Interaction with model phospholipid membranes of lupin seed γ-conglutin, a glycaemia-lowering protein from Lupinus albus seeds, has been studied by means of Fourier-Transform infrared spectroscopy at p2H 7.0 and at p2H 4.5. The protein maintains the same secondary structure both at p2H 7.0 and at p2H 4.5, but at p2H 7.0 a higher 1H/2H exchange was observed, indicating a greater solvent accessibility. The difference in T m and T D1/2 of the protein at the abovementioned p2H's has been calculated around 20 °C. Infrared measurements have been then performed in the presence of DMPG and DOPA at p2H 4.5. DMPG showed a little destabilizing effect while DOPA exerted a great stabilizing effect, increasing the T m of γ-conglutin at p2H 4.5 of more than 20 °C. Since γ-conglutin at p2H 4.5 is in the monomeric form, the interaction with DOPA likely promotes the oligomerization even at p2H 4.5. Interaction between DMPG or DOPA and γ-conglutin has been confirmed by turbidity experiments with DMPC:DMPG or DOPC:DOPA SUVs. Turbidity data also showed high-affinity binding of γ-conglutin to anionic SUVs made up with DOPA. The molecular features outlined in this study are relevant to address the applicative exploitation and to delineate a deeper comprehension of the natural functional role of γ-conglutin. Highlights • γ-conglutin when orally administered in humans and animals significantly decrease glycaemia. • Structure, thermal stability, interaction and oligomerization status with SUVs has been studied by spectroscopic method. • DOPA exerts a great stabilizing effect on thermal stability, probably by promoting oligomerization. • High-affinity binding of γ-conglutin to anionic SUVs with DOPA has been observed. • Stabilizing and protective effects of SUVs may be useful carriers for nutraceutical applications of γ-conglutin. [ABSTRACT FROM AUTHOR]