Changes in Structure and in Interactions of Heat-Treated Bovine β-Lactoglobulin

Abstract

Heat stress on structure and ligand binding of beta-LG has been studied by fluorescence, circular dichroism and gel electrophoresis at pH 6.5. Native PAGE gel electrophoresis shows that denaturation of beta-LG is reversible up to 75 degrees C then it becomes irreversible due to aggregation of beta-LG. Formation of aggregated beta-LG is completed at 95 degrees C. Circular dichroism results indicate that formation of aggregated beta-LG is accompanied by the scrambling of disulfide bonds (creation of new intramolecular and intermolecular disulfide bridges and rearrangement of old intramolecular disulfide bridges). Addition of ethanolic retinol causes a change in polarity of the solution and favors transformation of the beta<-->alpha structure. In the presence of retinol, the alpha-helix content of the secondary structure of heat-treated beta-LG is increased and the major portion of its secondary structure is helical. Fluorescence results show that heat-treated beta-LG at 95 degrees C can still bind retinol. The refolding of the tertiary structure of beta-LG heat-denatured at 95 degrees C may recreate a retinol binding site. Surprisingly, the affinity of the new site for retinol is higher than that of native beta-LG; however, the apparent molar ratio is lower than one. The binding properties of beta-LG for terpenoids have been measured after its heat treatment at 20, 75 and 95 degrees C. The intensity of tryptophan emission at 330 nm was changed only in the case of the interaction with beta-ionone. Other ligands probably cannot bind to beta-LG or they bind in a binding site far from the tryptophan residues, hence not affecting its fluorescence.

Structural changes and allergenic properties of β‐lactoglobulin upon exposure to high‐intensity ultrasound

“…It was also apparent that this form of BLG almost completely lost capacity to bind retinol. A similar behavior has been described for heating induced conformational changes in BLG where a minor population of heat-treated/denaturated BLG refolded to the native conformation and was able to bind retinol with the binding constant of a native protein [33]. On the other hand, BLG oligomers formation during heating treatments at higher temperatures than in our study prevented retinol binding [20].…”

Complejos vitamina E-β-lactoglobulina incluidos en películas biopoliméricas de alginato de sodio

“…El calentamiento a temperaturas superiores a 80 °C provoca cambios en la estructura secundaria y terciaria de la proteína, ocasionando la pérdida de la cavidad interna aunque conserva parte de su actividad encapsulante. Esto último sugiere que se crean nuevos sitios de unión tras exponer al solvente otros residuos hidrofóbicos (Mousavi, et al, 2008).…”

Extrusion Texturized Dairy Proteins

“…a-LA and b-LG are globular proteins whose structures normally begin to change at 50 and 80 C, respectively (Farrell et al, 2002). As a-LA and b-LG denature, the proteins unfold and SH groups are exposed and undergo possible interchange (Mousavi et al, 2008;Patel et al, 2006). As a-LA and b-LG denature, the proteins unfold and SH groups are exposed and undergo possible interchange (Mousavi et al, 2008;Patel et al, 2006).…”