The main goal of this work is to investigate the conformational changes of the receptor upon binding of a ligand as well as an inhibitor. The estrogen receptor is one of the ligand-activated gene regulatory proteins which constitute the steroid-hormone receptor superfamily. This family of proteins are made of three distinct domains, N-term, DNA-binding, and ligand-binding domains. In the absence of hormone (ligand), the unliganded steroid receptor is associated with the heat shock protein, which may facilitate hormone binding as well as inactivate the DNA binding and/or transactivation functions of steroid receptors. A large conformational change is known to hormone receptors upon binding of steroid hormone. We are currently expressing and purifying the ligand-binding domain of the estrogen receptor. Our immediate goal is to study the solution structure of this protein by multi-dimensional NMR, using N15, C13 labeled, perdeuterated samples. During the structural determination process, we anticipate an extensive use of computational and graphics tools including Sparky, Mardigras/Corma (Complete Relaxation Matrix Analysis), MidasPlus and Chimera, Amber, and X-PLOR.