TY - JOUR
T1 - A unified structural model of the mammalian translocator protein (TSPO)
AU - Xia, Yan
AU - Ledwitch, Kaitlyn
AU - Kuenze, Georg
AU - Duran, Amanda
AU - Li, Jun
AU - Sanders, Charles R.
AU - Manning, Charles
AU - Meiler, Jens
N1 - Funding Information:
This work was conducted using the computing cluster of the Advanced Center for Research and Education (ACCRE) at Vanderbilt University, TN. Work in the Meiler laboratory is supported through NIH (R01 GM080403, R01 GM099842) and NSF (CHE 1305874). CRS was supported by NIH RF1 AG056147. VUIIS8310 was developed with support from NIH R01 CA163806 (HCM) and the Kleberg Foundation (HCM). The authors would also like to thank Dr. Markus Voehler and the Biomolecular NMR Facility at Vanderbilt for support and advice regarding the NMR data acquisition.
Publisher Copyright:
© 2019, Springer Nature B.V.
PY - 2019/7/15
Y1 - 2019/7/15
N2 - The translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), is a membrane protein located on the outer mitochondrial membrane. Experimentally-derived structures of mouse TSPO (mTSPO) and its homologs from bacterial species have been determined by NMR spectroscopy and X-ray crystallography, respectively. These structures and ligand interactions within the TSPO binding pocket display distinct differences. Here, we leverage experimental and computational studies to derive a unified structural model of mTSPO in the presence and absence of the TSPO ligand, PK11195, and study the effects of DPC detergent micelles on the TSPO structure and ligand binding. From this work, we conclude that that the lipid-mimetic system used to solubilize mTSPO for NMR studies thermodynamically destabilizes the protein, introduces structural perturbations, and alters the characteristics of ligand binding. Furthermore, we used Rosetta to construct a unified mTSPO model that reconciles deviating features of the mammalian and bacterial TSPO. These deviating features are likely a consequence of the detergent system used for structure determination of mTSPO by NMR. The unified mTSPO model agrees with available experimental NMR data, appears to be physically realistic (i.e. thermodynamically not frustrated as judged by the Rosetta energy function), and simultaneously shares the structural features observed in sequence-conserved regions of the bacterial proteins. Finally, we identified the binding site for an imaging ligand VUIIS8310 that is currently positioned for clinical translation using NMR spectroscopy and propose a computational model of the VUIIS8310-mTSPO complex.
AB - The translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), is a membrane protein located on the outer mitochondrial membrane. Experimentally-derived structures of mouse TSPO (mTSPO) and its homologs from bacterial species have been determined by NMR spectroscopy and X-ray crystallography, respectively. These structures and ligand interactions within the TSPO binding pocket display distinct differences. Here, we leverage experimental and computational studies to derive a unified structural model of mTSPO in the presence and absence of the TSPO ligand, PK11195, and study the effects of DPC detergent micelles on the TSPO structure and ligand binding. From this work, we conclude that that the lipid-mimetic system used to solubilize mTSPO for NMR studies thermodynamically destabilizes the protein, introduces structural perturbations, and alters the characteristics of ligand binding. Furthermore, we used Rosetta to construct a unified mTSPO model that reconciles deviating features of the mammalian and bacterial TSPO. These deviating features are likely a consequence of the detergent system used for structure determination of mTSPO by NMR. The unified mTSPO model agrees with available experimental NMR data, appears to be physically realistic (i.e. thermodynamically not frustrated as judged by the Rosetta energy function), and simultaneously shares the structural features observed in sequence-conserved regions of the bacterial proteins. Finally, we identified the binding site for an imaging ligand VUIIS8310 that is currently positioned for clinical translation using NMR spectroscopy and propose a computational model of the VUIIS8310-mTSPO complex.
KW - Homology modeling
KW - Ligand docking
KW - NMR spectroscopy
KW - Protein folding
KW - Rosetta
KW - Translocator protein (TSPO)
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U2 - 10.1007/s10858-019-00257-1
DO - 10.1007/s10858-019-00257-1
M3 - Article
C2 - 31243635
AN - SCOPUS:85068210911
SN - 0925-2738
VL - 73
SP - 347
EP - 364
JO - Journal of Biomolecular NMR
JF - Journal of Biomolecular NMR
IS - 6-7
ER -