Binding of Per- and Polyfluoroalkyl Substances to β-Lactoglobulin from Bovine Milk

Per- and polyfluoroalkyl substances (PFAS) are known for their high environmental persistence and potential toxicity. The presence of PFAS has been reported in many dairy products. However, the mechanisms underlying PFAS accumulation in these products and the impact of these contaminants on milk protein function remain unclear. Here, we used native mass spectrometry and molecular dynamics simulations to probe the interactions between 19 PFAS of environmental concern and two isoforms of the major bovine whey protein β-lactoglobulin (β-LG). We observed that six of these PFAS bound to both protein isoforms with low to mid-micromolar dissociation constants. Based on competitive binding experiments with endogenous ligands, PFAS can bind orthosterically and preferentially to β-LG’s hydrophobic ligand-binding calyx. Interestingly, we also observed that β-cyclodextrin can suppress PFAS binding to β-LG, owing to the ability of β-cyclodextrin to directly sequester PFAS from solution. Together, this research sheds light on PFAS—β-LG binding, suggesting that such interactions could impact lipid/fatty acid transport in bovine mammary glands. Furthermore, our results highlight the potential use of β-cyclodextrin in mitigating PFAS binding, providing insights towards the development of strategies to reduce PFAS accumulation in dairy products and other biological systems.