College of Health and Life Sciences, Aston University, Birmingham B4 7ET, U.K.
Biochem Soc Trans. 2021 Jun 30;49(3):1349-1359. doi: 10.1042/BST20201067.
In the twelve years since styrene maleic acid (SMA) was first used to extract and purify a membrane protein within a native lipid bilayer, this technological breakthrough has provided insight into the structural and functional details of protein-lipid interactions. Most recently, advances in cryo-EM have demonstrated that SMA-extracted membrane proteins are a rich-source of structural data. For example, it has been possible to resolve the details of annular lipids and protein-protein interactions within complexes, the nature of lipids within central cavities and binding pockets, regions involved in stabilising multimers, details of terminal residues that would otherwise remain unresolved and the identification of physiologically relevant states. Functionally, SMA extraction has allowed the analysis of membrane proteins that are unstable in detergents, the characterization of an ultrafast component in the kinetics of electron transfer that was not possible in detergent-solubilised samples and quantitative, real-time measurement of binding assays with low concentrations of purified protein. While the use of SMA comes with limitations such as its sensitivity to low pH and divalent cations, its major advantage is maintenance of a protein's lipid bilayer. This has enabled researchers to view and assay proteins in an environment close to their native ones, leading to new structural and mechanistic insights.
自苯乙烯马来酸（SMA）首次用于从天然脂质双层中提取和纯化膜蛋白以来，已经过去了十二年。这一技术突破为研究蛋白质-脂质相互作用的结构和功能细节提供了新的思路。最近，冷冻电镜技术的进步表明，SMA 提取的膜蛋白是结构数据的丰富来源。例如，已经有可能解析出复合物中环状脂质和蛋白质-蛋白质相互作用的细节、中心腔和结合口袋内脂质的性质、稳定多聚体的区域、原本无法解析的末端残基的细节以及鉴定生理相关状态。从功能上讲，SMA 提取允许分析在去污剂中不稳定的膜蛋白，对电子转移动力学中超快组分进行表征，这在去污剂溶解的样品中是不可能的，并且可以对低浓度纯化蛋白的结合测定进行定量、实时测量。尽管 SMA 的使用存在一些限制，例如对低 pH 值和二价阳离子的敏感性，但它的主要优势是保持蛋白质的脂质双层。这使研究人员能够在接近天然环境的情况下观察和检测蛋白质，从而获得新的结构和机制见解。
