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Open AccessArticle

Characterization of the High-Affinity Drug Ligand Binding Site of Mouse Recombinant TSPO

1
Sorbonne Université, Ecole Normale Supérieure, PSL University, CNRS, Laboratoire des Biomolécules (LBM), 4 place Jussieu, F-75005 Paris, France
2
Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2019, 20(6), 1444; https://doi.org/10.3390/ijms20061444
Received: 4 February 2019 / Revised: 18 March 2019 / Accepted: 19 March 2019 / Published: 21 March 2019
The optimization of translocator protein (TSPO) ligands for Positron Emission Tomography as well as for the modulation of neurosteroids is a critical necessity for the development of TSPO-based diagnostics and therapeutics of neuropsychiatrics and neurodegenerative disorders. Structural hints on the interaction site and ligand binding mechanism are essential for the development of efficient TSPO ligands. Recently published atomic structures of recombinant mammalian and bacterial TSPO1, bound with either the high-affinity drug ligand PK 11195 or protoporphyrin IX, have revealed the membrane protein topology and the ligand binding pocket. The ligand is surrounded by amino acids from the five transmembrane helices as well as the cytosolic loops. However, the precise mechanism of ligand binding remains unknown. Previous biochemical studies had suggested that ligand selectivity and binding was governed by these loops. We performed site-directed mutagenesis to further test this hypothesis and measured the binding affinities. We show that aromatic residues (Y34 and F100) from the cytosolic loops contribute to PK 11195 access to its binding site. Limited proteolytic digestion, circular dichroism and solution two-dimensional (2-D) NMR using selective amino acid labelling provide information on the intramolecular flexibility and conformational changes in the TSPO structure upon PK 11195 binding. We also discuss the differences in the PK 11195 binding affinities and the primary structure between TSPO (TSPO1) and its paralogous gene product TSPO2. View Full-Text
Keywords: translocator protein (TSPO); ligand binding site; nuclear magnetic resonance (NMR); trypsin digestion; circular dichroism (CD); intrinsic fluorescence translocator protein (TSPO); ligand binding site; nuclear magnetic resonance (NMR); trypsin digestion; circular dichroism (CD); intrinsic fluorescence
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MDPI and ACS Style

Iatmanen-Harbi, S.; Senicourt, l.; Papadopoulos, V.; Lequin, O.; Lacapere, J.-J. Characterization of the High-Affinity Drug Ligand Binding Site of Mouse Recombinant TSPO. Int. J. Mol. Sci. 2019, 20, 1444. https://doi.org/10.3390/ijms20061444

AMA Style

Iatmanen-Harbi S, Senicourt l, Papadopoulos V, Lequin O, Lacapere J-J. Characterization of the High-Affinity Drug Ligand Binding Site of Mouse Recombinant TSPO. International Journal of Molecular Sciences. 2019; 20(6):1444. https://doi.org/10.3390/ijms20061444

Chicago/Turabian Style

Iatmanen-Harbi, Soria; Senicourt, lucile; Papadopoulos, Vassilios; Lequin, Olivier; Lacapere, Jean-Jacques. 2019. "Characterization of the High-Affinity Drug Ligand Binding Site of Mouse Recombinant TSPO" Int. J. Mol. Sci. 20, no. 6: 1444. https://doi.org/10.3390/ijms20061444

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