In Situ Structural Studies of Anabaena Sensory Rhodopsin in the E. coli Membrane
In Situ Structural Studies of Anabaena Sensory Rhodopsin in the E. coli Membrane
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大肠杆菌膜中鱼腥藻感觉视紫红质的原位结构研究
DOI：
10.1016/j.bpj.2015.02.018
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发表时间：
2015
影响因子：
3.4
通讯作者：
Ladizhansky, Vladimir
中科院分区：
文献类型：
--
作者：
Ward, Meaghan E.;Wang, Shenlin;Munro, Rachel;Ritz, Emily;Hung, Ivan;Gor’kov, Peter L.;Jiang, Yunjiang;Liang, Hongjun;Brown, Leonid S.;Ladizhansky, Vladimir
魔角自旋核磁共振非常适合于研究类脂环境中的膜蛋白。然而，天然细胞膜总是比最常用的固体核磁共振(SSNMR)研究中使用的蛋白质脂质体更复杂，差异可能会影响所研究蛋白质的结构和动力学。在这项工作中，我们使用SS核磁共振和其他生化和生物物理方法来研究在大肠杆菌内膜中制备的七跨膜螺旋光感受器Anabaenasensory视紫红质(ASR)的结构，并将其与DMPC/DMPA脂类形成的双层膜中的结构进行比较。我们发现ASR在两种环境中都被组织成三聚体，但形成了不同对称性的二维晶格。它有利于脂质体中的六角形填充，但也可能在体内形成正方形的晶格。为了研究结构位置可能的变化，我们进行了二维和三维SS核磁共振实验，并分析了化学位移和峰强度的差异。总体而言，这一分析揭示了ASR的结构在大肠杆菌的内膜中很大程度上是保守的，蛋白脂质体中以前在ASR中观察到的视紫红质的许多重要结构特征被保留了下来。由于膜的变化，蛋白质结构发生了微小的、特定于部位的扰动，这表明蛋白质可以巧妙地适应环境，而不需要进行大的结构重排。
Magic-angle spinning nuclear magnetic resonance is well suited for the study of membrane proteins in the nativelike lipid environment. However, the natural cellular membrane is invariably more complex than the proteoliposomes most often used for solid-state NMR (SSNMR) studies, and differences may affect the structure and dynamics of the proteins under examination. In this work we use SSNMR and other biochemical and biophysical methods to probe the structure of a seven-transmembrane helical photoreceptor,Anabaenasensory rhodopsin (ASR), prepared in theEscherichia coliinner membrane, and compare it to that in a bilayer formed by DMPC/DMPA lipids. We find that ASR is organized into trimers in both environments but forms two-dimensional crystal lattices of different symmetries. It favors hexagonal packing in liposomes, but may form a square lattice in theE. colimembrane. To examine possible changes in structure site-specifically, we perform two- and three-dimensional SSNMR experiments and analyze the differences in chemical shifts and peak intensities. Overall, this analysis reveals that the structure of ASR is largely conserved in the inner membrane ofE. coli, with many of the important structural features of rhodopsins previously observed in ASR in proteoliposomes being preserved. Small, site-specific perturbations in protein structure that occur as a result of the membrane changes indicate that the protein can subtly adapt to its environment without large structural rearrangement.