UVB pretreatment of & beta;-lactoglobulin affects the temperature-induced formation of functional amyloid-like aggregates and promotes oxidative degradation

Unfolding in combination with or without acid hydrolysis is crucial for the formation of functional amyloid (fibrillar) or amyloid-like (worm-like) & beta;-lactoglobulin (BLG) aggregates, which can be induced through temperature treatment for several hours at pH 2-4. A preceding conformational destabilization of BLG might affect its aggregation. We investigated ultraviolet (UV) B radiation as conformational perturbing treatment to facilitate temperature-induced protein aggregation.2-h UVB pretreated BLG (UV-BLG) exhibited an accelerated worm-like aggregation at pH 3.5, while at pH 2 the formation of fibrils was decelerated. The UV-induced conformational destabilization lowered the thermal stability and thus facilitates unfolding during thermal treatment. Thereby, the formation of covalent and non covalent intermolecular interactions was favored, which promoted assembly of intact proteins resulting in worm-like aggregates. The oxidative degradation of UV-BLG was suggested to alter fibrillation-prone protein regions and thereby impede peptide assembly.

Automated summary

Unfolding, with or without acid hydrolysis, is necessary for the formation of functional amyloid or amyloid-like β-lactoglobulin aggregates induced by temperature treatment at pH 2-4. UVB radiation can be used as a conformational perturbing treatment to promote protein aggregation by destabilizing the protein structure. UV-treated BLG exhibited accelerated worm-like aggregation at pH 3.5 and decelerated fibril formation at pH 2. The UV-induced conformational destabilization enhanced the unfolding process during thermal treatment, favoring the formation of covalent and non-covalent intermolecular interactions and resulting in worm-like aggregates. Oxidative degradation of UV-treated BLG hindered peptide assembly by altering fibrillation-prone protein regions.