Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
Structure. 2010 Jun 9;18(6):677-87. doi: 10.1016/j.str.2010.03.001.
The 18 kDa TSPO protein is a polytopic mitochondrial outer membrane protein involved in a wide range of physiological functions and pathologies, including neurodegeneration and cancer. The pharmacology of TSPO has been extensively studied, but little is known about its biochemistry, oligomeric state, and structure. We have expressed, purified, and characterized a homologous protein, TspO from Rhodobacter sphaeroides, and reconstituted it as helical crystals. Using electron cryomicroscopy and single-particle helical reconstruction, we have determined a three-dimensional structure of TspO at 10 A resolution. The structure suggests that monomeric TspO comprises five transmembrane alpha helices that form a homodimer, which is consistent with the dimeric state observed in detergent solution. Furthermore, the arrangement of transmembrane domains of individual TspO subunits indicates a possibility of two substrate translocation pathways per dimer. The structure provides the first insight into the molecular architecture of TSPO/PBR protein family that will serve as a framework for future studies.
18kDa TSPO 蛋白是一种多跨线粒体外膜蛋白，参与广泛的生理功能和病理学，包括神经退行性变和癌症。TSPO 的药理学已经得到了广泛的研究，但对其生物化学、寡聚状态和结构知之甚少。我们已经表达、纯化和表征了 Rhodobacter sphaeroides 的同源蛋白 TspO，并将其重组为螺旋晶体。使用电子 cryomicroscopy 和单颗粒螺旋重建，我们确定了 TspO 的三维结构，分辨率为 10A。该结构表明单体 TspO 由五个跨膜α螺旋组成，形成同源二聚体，这与在去污剂溶液中观察到的二聚体状态一致。此外，单个 TspO 亚基的跨膜结构域的排列表明每个二聚体可能有两种底物转运途径。该结构首次提供了 TSPO/PBR 蛋白家族的分子结构的见解，将作为未来研究的框架。
