Characterizing the structure of styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) using RAFT polymerization for membrane protein spectroscopic studies
Characterizing the structure of styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) using RAFT polymerization for membrane protein spectroscopic studies
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DOI：
10.1016/j.chemphyslip.2018.12.002
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发表时间：
2019-01-01
影响因子：
3.4
通讯作者：
Lorigan, Gary A.
中科院分区：
文献类型：
--
作者：
Harding, Benjamin D.;Dixit, Gunjan;Lorigan, Gary A.
膜蛋白在维持机体的结构和生理方面起着重要的作用。尽管膜蛋白具有重要意义，但由于难以模拟其天然脂质双分子层环境，涉及膜蛋白的光谱研究仍然具有挑战性。膜模拟系统，如洗涤剂胶束、脂质体、双胞体、纳米盘、脂碟等，在结构研究中改善了膜蛋白的溶解性和折叠特性，然而，每种模拟系统都有其自身的局限性。在本研究中，使用三种不同的脂质环境，用苯乙烯-马来酸（StMA）共聚物滴定囊泡，得到重量比为1:1.5的均匀smallp体系（类似于10 nm）（囊泡：StMA溶液）。采用动态光散射（DLS）和透射电子显微镜（TEM）相结合的方法对这些SMALPs进行了表征。我们采用可控的合成机制合成了StMA基嵌段共聚物，称为可逆加成-破碎链转移聚合（RAFT） SMALPs。将KCNQ1 （Q1-VSD）的电压传感器结构域整合到RAFT SMALPs中，表明该系统在利用不同生物物理技术研究膜蛋白方面具有广阔的应用前景。Q1-VSD中疏水区对应的V165C被纳入smallp体系。连续波电子顺磁共振（CW-EPR）线形分析显示线形变宽，显示出自旋标签的刚性成分较低，速度成分较快。
Membrane proteins play an important role in maintaining the structure and physiology of an organism. Despite their significance, spectroscopic studies involving membrane proteins remain challenging due to the difficulties in mimicking their native lipid bilayer environment. Membrane mimetic systems such as detergent micelles, liposomes, bicelles, nanodiscs, lipodisqs have improved the solubility and folding properties of the membrane proteins for structural studies, however, each mimetic system suffers from its own limitations. In this study, using three different lipid environments, vesicles were titrated with styrene-maleic acid (StMA) copolymer leading to a homogeneous SMALP system (similar to 10 nm) at a weight ratio of 1:1.5 (vesicle: StMA solution). A combination of Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) was used to characterize these SMALPs. We used a controlled synthesis mechanism to synthesize StMA based block copolymers called reversible addition-fragmentation chain transfer polymerization (RAFT) SMALPs. Incorporation of the Voltage Sensor Domain of KCNQ1 (Q1-VSD) into RAFT SMALPs indicates that this is a promising application of this system to study membrane proteins using different biophysical techniques. V165C in Q1-VSD corresponding to the hydrophobic region was incorporated into the SMALP system. Continuous Wave-Electron Paramagnetic Resonance (CW-EPR) line shape analysis showed line shape broadening, exposing a lower rigid component and a faster component of the spin label.