Accurate 3D structures of membrane proteins are essential for comprehending their mechanisms of action and designing specific ligands to modulate their activities. However, these structures are still uncommon due to the involvement of detergents in the sample preparation. Recently, membrane-active polymers have emerged as an alternative to detergents, but their incompatibility with low pH and divalent cations has hindered their efficacy. Herein, we describe the design, synthesis, characterization, and application of a new class of pH-tunable membrane-active polymers, NCMNP2a-x. The results demonstrated that NCMNP2a-x could be used for high-resolution single-particle cryo-EM structural analysis of AcrB in various pH conditions and can effectively solubilize BcTSPO with the function preserved. Molecular dynamic simulation is consistent with experimental data that shed great insights into the working mechanism of this class of polymers. These results demonstrated that NCMNP2a-x might have broad applications in membrane protein research.

中文翻译：

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pH 可调膜活性聚合物 NCMNP2a-x 及其潜在的膜蛋白应用

膜蛋白的准确 3D 结构对于理解其作用机制和设计特定配体来调节其活性至关重要。然而，由于样品制备中涉及去污剂，这些结构仍然不常见。最近，膜活性聚合物已成为洗涤剂的替代品，但它们与低 pH 值和二价阳离子的不相容性阻碍了它们的功效。在此，我们描述了一类新型 pH 可调膜活性聚合物 NCMNP2ax 的设计、合成、表征和应用。结果表明，NCMNP2a- x可用于各种pH条件下AcrB的高分辨率单颗粒冷冻电镜结构分析，并能有效溶解Bc TSPO并保留功能。分子动力学模拟与实验数据一致，为此类聚合物的工作机制提供了深入的见解。这些结果表明 NCMNP2ax在膜蛋白研究中可能具有广泛的应用。