Structure of the mammalian TSPO/PBR protein

The 3D structure of the 18-kDa transmembrane (TM) protein TSPO (translocator protein)/PBR (peripheral benzodiazepine receptor), which contains a binding site for benzodiazepines, is important to better understand its function and regulation by endogenous and synthetic ligands. We have recently determined the structure of mammalian TSPO/PBR in complex with the diagnostic ligand PK11195 [1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide; Jaremko et al. (2014) Science 343, 1363–1366], providing for the first time atomic-level insight into the conformation of this protein, which is up-regulated in various pathological conditions including Alzheimer's disease and Parkinson's disease. Here, we review the studies which have probed the structural properties of mammalian TSPO/PBR as well as the homologues bacterial tryptophan-rich sensory proteins (TspOs) over the years and provide detailed insight into the 3D structure of mouse TSPO (mTSPO)/PBR in complex with PK11195.