Versatile Copurification Procedure for Rapid Isolation of Homogeneous RAR-RXR Heterodimers

RAR-RXR heterodimeric complexes (RARαΔAB-RXRαΔAB) bound to cognate DR5 DNA response elements were purified to apparent structural and functional homogeneity using a novel versatile immobilized metal affinity chromatography (IMAC) copurification procedure. Dynamic light scattering studies indicated that the complexes were more than 85% monodisperse. By electron microscopy the negatively stained RAR-RXR–DNA complexes appeared homogeneous and corresponded to a dimeric arrangement of the molecules. Using heterodimers purified according to this procedure we demonstrate ligand binding of RXR in the context of the RAR-RXR heterodimer–DNA complex. The present copurification procedure is rapid and has yielded high quality heterodimer–DNA complexes suitable for both structural and biochemical studies.