title: Structural changes in emulsion-bound bovine beta-lactoglobulin affect its proteolysis and immunoreactivity.
abstract: Adsorption on the surface of sub-micrometric oil droplets resulted in significant changes in the tertiary structure of bovine beta-lactoglobulin (BLG), a whey protein broadly used as a food ingredient and a major food allergen. The adsorbed protein had increased sensitivity to trypsin, and increased immunoreactivity towards specific monoclonal antibodies. In spite of the extensive tryptic breakdown of emulsion-bound BLG, some sequence stretches in BLG became trypsin-insensitive upon absorption of the protein on the fat droplets. As a consequence - at contrast with free BLG - proteolysis of emulsion-bound BLG did not decrease the immunoreactivity of the protein, and some of the large peptides generated by trypsinolysis of emulsion-bound BLG were still recognizable by specific monoclonal antibodies. Structural changes occurring in emulsion-bound BLG and their consequences are discussed in comparison with those occurring when the tertiary structure of BLG is modified by lipophilic salts, by urea, or upon interaction with solid hydrophobic surfaces. Such a comparison highlights the relevance of situation-specific structural modifications, that in turn may affect physiologically relevant features of the protein.
authors.affiliation: Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via G. Celoria 2, 20133 Milano, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Marengo
authors.affiliation: Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via G. Celoria 2, 20133 Milano, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Miriani
authors.affiliation: Department of Agriculture, University of Naples, Via Università 100, 80055 Portici, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Ferranti
authors.affiliation: Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via G. Celoria 2, 20133 Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bonomi
authors.affiliation: Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via G. Celoria 2, 20133 Milano, Italy. Electronic address: stefania.iametti@unimi.it.
authors.forename: Stefania
authors.initials: S
authors.lastname: Iametti
authors.affiliation: Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via G. Celoria 2, 20133 Milano, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Barbiroli
mesh_terms: D000327:Adsorption; D004655:Emulsions; D004797:Enzyme-Linked Immunosorbent Assay; D007782:Lactoglobulins / Q000737:chemistry* / Q000276:immunology; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence
chemical_list: D004655:Emulsions; D007782:Lactoglobulins
keywords: Beta-lactoglobulin; Food allergens; Immunoreactivity; Liquid/liquid interfaces; Proteins