Per- and polyfluoroalkyl substances (PFAS) pose significant health risks due to their widespread presence in various environmental and biological matrices. However, the molecular-level mechanisms underlying the interactions between PFAS and biological constituents, including proteins, carbohydrates, lipids, and DNA, remain poorly understood. Here, we investigate the interactions between a legacy PFAS, viz. perfluorooctanoic acid (PFOA), and the milk protein β-lactoglobulin (BLG) obtained using a combination of experimental and computational techniques. Circular dichroism studies reveal that PFOA perturbs the secondary structure of BLG, by driving a dose-dependent loss of α-helicity and alterations in its β-sheet content. Furthermore, exposure of the protein to PFOA attenuates the on-rate constant for the binding of the hydrophobic probe 8-anilino-1-naphthalene sulfonic acid (ANS), suggesting potential functional impairment of BLG by PFOA. Steered molecular dynamics and umbrella sampling calculations reveal that PFOA binding leads to the formation of an energetically favorable novel binding pocket within the protein, when residues 129–142 are steered to unfold from their initial α-helical structure, wherein a host of intermolecular interactions between PFOA and BLG’s residues serve to insert the PFOA into the region between the unfolded helix and beta-sheets. Together, the data provide a novel understanding of the atomic and molecular mechanism(s) by which PFAS modulates structure and function in a globular protein, leading to a beginning of our understanding of altered biological outcomes.

中文翻译：

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从原子和分子角度洞察 PFOA 如何降低 α 螺旋度、损害底物结合以及在球状蛋白模型中创建结合袋

全氟烷基物质和多氟烷基物质 (PFAS) 由于广泛存在于各种环境和生物基质中而造成严重的健康风险。然而，PFAS 与生物成分（包括蛋白质、碳水化合物、脂质和 DNA）之间相互作用的分子水平机制仍然知之甚少。在这里，我们研究了传统 PFAS 之间的相互作用，即。全氟辛酸（PFOA）和乳蛋白β-乳球蛋白（BLG）是通过实验和计算技术相结合获得的。圆二色性研究表明，PFOA 通过驱动剂量依赖性的 α 螺旋性损失和 β 片层含量的改变，扰乱 BLG 的二级结构。此外，蛋白质暴露于 PFOA 会减弱疏水性探针 8-苯胺基-1-萘磺酸 (ANS) 结合的结合速率常数，表明 PFOA 对 BLG 可能造成功能损害。引导分子动力学和伞式采样计算表明，当残基 129-142 被引导从其最初的 α 螺旋结构展开时，PFOA 结合会导致在蛋白质内形成一个能量上有利的新型结合袋，其中许多分子间相互作用PFOA 和 BLG 的残基用于将 PFOA 插入展开的螺旋和 β 折叠之间的区域。总之，这些数据为 PFAS 调节球状蛋白的结构和功能的原子和分子机制提供了新的理解，使我们开始了解改变的生物学结果。