Effects of temperature, pH and sugar binding on the structures of lectins ebulin f and SELfd

Ebulin f and SELfd are two lectins of Sambucus ebulus L. that show different stability and digestibility properties in gastric fluid due to their structural differences which may explain their different toxicological profiles. The main aim was to determine the effects of pH, temperature and sugar binding on the intrinsic structures of both proteins by fluorescence analyses. Quenching experiments were conducted, under different pH and temperature conditions, with acrylamide (uncharged) and iodide (charged), to study the possible changes of their intrinsic fluorescence. Results revealed that the native structure of SELfd is more folded than that of ebulin f. At pH 2.0, ebulin f displayed a more open structure than at neutral pH. It can be concluded that this is the main reason why ebulin f is accessible to pepsin action and more sensitive to degradation, in contrast to SELfd as we reported previously. (C) 2016 Elsevier Ltd. All rights reserved.