Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data and Computer Simulations

Poster Abstracts

69-POS Board 29 Coregulators Select Conformational States from Drug Specific Peroxisome Proliferator- activated Receptor Gamma (PPARγ) Conformational Ensembles Michelle Nemetchek 1,2,3 , Ian M. Chrisman 1,2 , Travis S. Hughes 1,2,3 . 2 The University of Montana, Missoula, MT, USA, 1 The University of Montana, Missoula, MT, USA, 3 The University of Montana, Missoula, MT, USA. Nuclear receptors are transcription factors that, when bound to agonists, cause transcription of regulatory genes. Peroxisome Proliferator-activated receptor gamma (PPARγ) is a nuclear receptor that is an important target of many FDA-approved type II diabetes drugs. When agonist bound, PPARγ recruits the coactivator Mediator complex subunit 1 (MED1), which is part of the mediator complex and triggers transcription of PPARγ-regulated genes. These genes control adipogenesis and lipid storage, and may enhance insulin sensitivity. When bound to inverse agonists, PPARγ complexes with Nuclear Receptor Corepressor I (NCoR1) and is blocked from transcriptional activation. By using Time-Resolved Förster Resonance Energy Transfer (TR- FRET), PPARγ binding drugs are shown to produce differing affinities for MED1 and NCoR1 peptides which contain the essential nuclear receptor binding motif. We covalently label PPARγ with a fluorine containing probe on the AF2 surface (the surface where coregulators have been demonstrated to interact) and use Fluorine-19 (19F) Nuclear Magnetic Resonance to determine how coregulator binding affects this surface. The AF2 surface conformations are highly similar for both full agonist bound and full agonist and MED1 co-bound states, similarly inverse agonists induce conformations that are relatively unchanged by NCoR1 binding. Our data also suggest that coregulators select conformations from a preexisting ensemble which is highly drug specific. This work links structure of the LBD to the functional outcome of transcription.

104