Antibodies against highly purified B-subunit of the chick oviduct progesterone receptor.

A rabbit was immunized with the highly purified B-subunit (110kDa) (20 to 50 micrograms per injection) of the chick oviduct progesterone receptor (PR). Specific antibodies (IgG-RB) were observed 2 weeks after the first booster injection and high antibody titers in the serum were found after the second and third booster injections (with Kdeq of interaction integral of 2 nM). IgG-RB were tested by immunoprecipitation, immunoblotting, density gradient ultracentrifugation and protein A-sepharose assay methods. They recognized not only the B-subunit but also the A-subunit (79K), the nuclear PR, the mero-receptor (proteolytic cleavage product) and the "non-activated" molybdate-stabilized "8S" PR. However, IgG-RB did not interact with the 90K non hormone-binding component of this 8S-PR. IgG-RB did not affect the binding of the hormone to PR, whether incubated with the receptor before or after labelling with tritiated progesterone. They did not cross-react with glucocorticosteroid receptor of the chick oviduct. Weak interaction was observed with estrogen receptor of the chick oviduct and with KC1 activated "4S" forms of the rabbit and human uterus PR.