Life & Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
Chemical Engineering & Applied Chemistry, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
Biochim Biophys Acta Biomembr. 2020 Jul 1;1862(7):183281. doi: 10.1016/j.bbamem.2020.183281. Epub 2020 Mar 21.
The use of styrene maleic acid co-polymer (SMA) for membrane protein extraction and purification has grown in recent years. SMA inserts in the membrane and assembles into small discs of bilayer encircled by polymer, termed SMA lipid particles (SMALPs). This allows purification of membrane proteins whilst maintaining their lipid bilayer environment. SMALPs offer several improvements over conventional detergent approaches, however there are limitations, most notably a sensitivity to low pH and divalent cations. Recently it was shown that the aliphatic diisobutylene-maleic acid (DIBMA) copolymer, was also able to directly solubilise membranes forming DIBMALPs (DIBMA lipid particles), and that this polymer overcame some of the limitations of SMA. In this study the ability of DIBMA to solubilise and purify functional membrane proteins has been compared to SMA. It was found that DIBMA is able to solubilise several different membrane proteins from different expression systems, however for some proteins it gives a lower yield and lower degree of purity than SMA. DIBMA extracted G protein-coupled receptors retain ligand- and G protein-binding. DIBMALPS are larger than SMALPs and display a decreased sensitivity to magnesium. However the stability of DIBMALPs appears to be lower than SMALPs. The lower purity and lower stability are likely linked to the larger size of the DIBMALP particle. However, this also offers a potentially less rigid lipid environment which may be more amenable to protein dynamics. Therefore the optimal choice of polymer will depend on which features of a protein are to be investigated.
近年来，苯乙烯马来酸共聚物（SMA）在膜蛋白提取和纯化中的应用日益增多。SMA 插入膜中并组装成双层的小圆盘，周围环绕着聚合物，称为 SMA 脂质体（SMALP）。这允许在保持其脂质双层环境的同时纯化膜蛋白。SMALP 相对于传统去污剂方法有几个优点，但是也存在一些局限性，最明显的是对低 pH 值和二价阳离子敏感。最近表明，脂肪族二异丁烯-马来酸（DIBMA）共聚物也能够直接溶解膜，形成 DIBMALP（DIBMA 脂质体），并且该聚合物克服了 SMA 的一些局限性。在这项研究中，比较了 DIBMA 溶解和纯化功能膜蛋白的能力与 SMA。结果发现，DIBMA 能够从不同的表达系统中溶解和纯化几种不同的膜蛋白，但是对于某些蛋白质，其产量和纯度均低于 SMA。从 DIBMA 中提取的 G 蛋白偶联受体保留配体和 G 蛋白结合能力。DIBMALP 比 SMALP 大，并且对镁的敏感性降低。但是，DIBMALP 的稳定性似乎低于 SMALP。较低的纯度和稳定性可能与 DIBMALP 颗粒的较大尺寸有关。然而，这也提供了一个潜在的不太刚性的脂质环境，可能更适合蛋白质动力学。因此，聚合物的最佳选择将取决于要研究的蛋白质的哪些特征。
