A thermodynamic model of RXR self-association and ligand binding

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
James Patrick Healy (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Vincent Henrich

Abstract: This study looked at the thermodynamics of ligand binding to the Retinoid X Receptor (RXR) and the formation of the RXR auto-repressive tetramer. Often called the "Master Coordinator" RXR is a required partner for activation of class II nuclear receptors. The first part used isothermal titration calorimetry (ITC) and site-directed mutagenesis to isolate and characterize the binding of a set of chemically diverse ligands to the RXR ligand binding domain. It was found that a molecule's shape and flexibility play a crucial role in determining a ligand's preference for the active or inactive form of RXR. These data showed that many RXR ligands appear to bind in a much stronger manner than was previously suggested by gene activation studies performed in cell culture. Furthermore it was shown that the shape of the potential ligand, whether it is bent or straight, as well as the amount of available molecular flexibility determine which RXR form a ligand will preferentially bind to The second part of the study used ITC and native-PAGE electrophoresis to model the formation and dissociation of the RXR tetramer. The initial model under consideration was a three stage model of monomer - dimer-tetramer equilibrium. However, non-linear curve fitting analysis of the proposed model to experimental data showed that RXR tetramer dissociation is much more exothermic than the model predicted. This led to a proposed more complex model for the tetramer formation which addresses the larger than expect energy release.

Additional Information

Language: English
Date: 2014
Isothermal Titration Calorimetry, Nuclear Receptor, RXR
Retinoid X receptors
Ligand binding (Biochemistry) $x Thermodynamics
Nuclear receptors (Biochemistry)
Site-specific mutagenesis

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