Reconstitution of the Steroid Receptor Heterocomplex.

Steroid receptors are members of a subfamily of the nuclear receptor superfamily. They play a dual role of steroid hormone receptors and transcription factors. Actually, these receptors are steroid-activated transcription factors. Classical soluble receptors exist as oligomeric complexes with the Hsp90-based chaperone machinery. The steroid receptor field was born and developed along with the molecular chaperone field. Chaperones are not exclusive partners associated to these receptors, but also comprise a large variety of heterocomplexes with other proteins involved in signal transduction. By using the glucocorticoid receptor (GR) as a standard model for most Hsp90-client proteins, in this chapter we describe the functional GR·Hsp90 heterocomplex assembly system from reticulocyte lysate or purified proteins.