[Structure of the progesterone receptor of chick oviduct. The 110 kDa B protein which binds the hormone has affinity for DNA].

Purified "B" protein (MW approximately 110 kDa) that binds progesterone, and more than 90% of the activated receptor labelled with tritiated hormone in the oviduct cytosol of chicks pretreated with estrogen have the same chromatography behavior on DNA-cellulose. Conversely, neither the nonactivated "8S" receptor, that includes the heat-shock protein hsp90, nor the later bind to DNA. With other biochemical and immunological arguments, these results indicate that the hormone binding B unit of the progesterone receptor binds DNA as do all steroid hormone receptors.