Structural and Biophysical Basis for PFAS Binding by Human Sterol Carrier Protein-2

Per- and polyfluoroalkyl substances (PFAS) are harmful environmental contaminants that bioaccumulate in human tissues and are linked to adverse health outcomes. While PFAS are known to bind to a variety of lipid binding proteins (LBPs), such as human serum albumin and fatty acid-binding proteins (FABPs), the broader molecular basis for their biological distribution and breadth of protein binding in humans remains unanswered. We hypothesize that some distribution and persistence of PFAS in humans arises from a distributed network of lipid transfer proteins that collectively solubilize and transport these compounds. To support this hypothesis, we investigated the interaction between various PFAS and human sterol carrier protein 2 (SCP2), a promiscuous, structurally distinct LBP with no previously reported binding with PFAS. Using a combination of screening, fluorescence displacement assays, protein structure prediction of PFAS-SCP2 complexes, and NMR experiments, we demonstrate for the first time that SCP2 is a PFAS-binding protein. Our findings establish SCP2 as a new PFAS-interacting protein, providing insights into the residues participating in these interactions and further supporting the hypothesis that PFAS engage with a broad network of LBPs to facilitate their distribution and persistence in the human body.