Steroid Hormone Binding to a Macromolecule from Hepatoma Tissue Culture Cells

A soluble, cytoplasmic, macromolecular steroid-binding fraction has been identified and partially purified from hepatoma tissue-cultured cells, a line of rat hepatoma cells in which tyrosine aminotransferase is induced by adrenal steroid hormones. Adrenal corticosteroids, progresterone, and 17α-hydroxyprogesterone form a strong association with the macromolecule which can be disrupted by heating the complex briefly at 65°. Treatment with proteolytic but not nucleolytic enzymes caused a slow release of the hormones, suggesting that the macromolecule is a protein. The binding substance was estimated to have an s20,w0 value of 2.6 by sucrose gradient centrifugation. The possible role of this component in cell function is discussed.