PFDA Influences the Structure of the Globular Milk Protein, α-Lactalbumin: Implications for Its Ability to Bind a Physiologically Crucial Cofactor

Abstract

Perfluorodecanoic acid (PFDA) ingestion is associated with liver, immune, developmental, and reproductive effects. Nevertheless, the molecular mechanisms underlying PFDA toxicity remain poorly understood. For example, despite its established presence in human milk, cow milk, and infant formula, its molecular interactions with constituent proteins and their consequences require further study. Here, we report the outcomes associated with the interaction between PFDA and α-lactalbumin (ALAC), a calcium-binding whey protein essential for nutrition and lactose production. Absorbance and Trp fluorescence data reveal PFDA-dependent changes consistent with interactions that perturb the native disposition of the optically active chromophores. Deconvolution of the amide I region of PFDA: protein IR spectra suggest dose-dependent distortions of PFDA in helical and sheet topologies. Ca²⁺-binding kinetics suggest that the “forever” chemical compromised metal-ion binding to the protein in a dose-dependent manner, reflecting impaired metal-dependent structural stabilization from the molten-globule-like apo-state to the native and biologically active holo-state. Molecular dynamics simulations identified two preferential PFDA binding regions enriched in hydrophobic and positively charged residues and showed that local rearrangements in ALAC’s unstructured N-terminus coils can generate tightly bound PFDA states with favorable interaction energies. Combined, these results reveal a coherent molecular mechanism in which PFDA anchors to the ALAC surface, disrupts secondary structure organization, and weakens Ca²⁺ binding. Considering ALAC’s role in early infant nutrition and human health, these findings provide a mechanistic insight into how PFAS exposure may compromise protein function in the postnatal environment.