 The mechanism of action of SRMs may vary depending on the chemical structure of the ligand and the receptor involved, however it is thought that many SRMs work by promoting a conformation of the receptor that is closely balanced between agonism and antagonism.In tissues where the concentration of coactivator proteins is higher than corepressors, the equilibrium is shifted in the agonist direction.Conversely in tissues where corepressors dominate, the ligand behaves as an antagonist.