Binding of alkylsulfonate ligands to bovine β-lactoglobulin: effects on protein denaturation by urea

• Published in: Food hydrocolloids 2005, Vol.19 (2), p.249-255
• Main Authors: Busti, Pablo, Scarpeci, Sonia, Gatti, Carlos A., Delorenzi, Néstor J.
• Format: Article
• Language: English
• Subjects: Beta-lactoglobulin; binding properties; binding sites; Biological and medical sciences; Chemical unfolding by urea; denaturation; Dissociation coupled unfolding (DCU) model; Fluorescence spectroscopy; Food additives; Food industries; food quality; Fundamental and applied biological sciences. Psychology; General aspects; hydrocolloids; Hydrophobic binding sites; hydrophobicity; lactoglobulins; Milk and cheese industries. Ice creams; protein binding; structure-activity relationships; sulfonates; urea
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2004.05.007

The effect of protein concentration on the interaction of alkylsulfonate ligands (AL n ), characterized by a similar sulfonate head and a progressively longer hydrocarbon tail (AL 8, AL 10, AL 12, AL 14 and AL 16), with bovine beta-lactoglobulin (β-LG) AB was studied using tryptophan fluorescence enhancement. Our results suggest that the AL n binding site is formed when β-LG monomers associates into dimers and that it is close to the junction region. The higher rigidity of β-LG structure observed on decreasing the pH, could be responsible for the loss of AL n binding at acid pH. The effects caused by AL n binding on β-LG denaturation by urea were also examined. The fraction of protein denatured was determined following λ max of fluorescence emission. The denaturation profiles were analyzed by the dissociation coupled unfolding model. Our results suggest that the protective action toward urea unfolding is exerted by a fraction of AL n bound to β-LG monomer, not related to the dimer existence. Moreover, we conclude that AL n mainly stabilizes the monomer structure.