Nuclear progesterone-binding protein in the guinea pig adrenal cortex: distinction from the classical progesterone receptor.
Nuclei purified from the guinea pig adrenal cortex contain a specific progesterone-binding activity which, based on enzyme degradation studies, appears to be proteinaceous. Saturation analysis revealed a Kd of about 15 nM and a binding capacity of about 33 pmol/mg DNA. The activity of the nuclear binding protein was specific essentially for progestational steroids; the two most potent progesterone competitors were 5 alpha-pregnane-3,20-dione and medroxyprogesterone (17 alpha-hydroxy-6 alpha-methylprogesterone), while 17 beta-estradiol, testosterone, cortisol, and other related steroids were poor competitors. The adrenocortical nuclear progesterone-binding protein was present to an equal extent in both male and female guinea pigs. The adrenocortical nuclear progesterone-binding protein differed from the classical progesterone receptor in that 1) the affinity of the adrenocortical binding protein for progesterone is an order of magnitude lower; 2) the potent synthetic progestin R5020 binds less tightly to the adrenocortical progesterone-binding protein; 3) the adrenocortical progesterone-binding protein is not modulated by estrogenic activity; 4) the adrenocortical progesterone-binding protein is more stable at 37 C; 5) the adrenocortical nuclear progesterone-binding protein is not salt extractable; and 6) Western blot analysis has revealed that an antiprogesterone receptor monoclonal antibody, which recognizes the guinea pig uterine classical nuclear progesterone receptor, does not recognize the adrenocortical nuclear progesterone-binding protein. Thus, the guinea pig adrenocortical nucleus contains a type of progesterone-binding protein that appears to be clearly different from the classical progesterone receptor.
Demura
T
T
Section on Adrenal Cell Biology, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Driscoll
W J
WJ
Strott
C A
CA
D000302:Adrenal Cortex / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D011374:Progesterone / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*
D004967:Estrogens; D011506:Proteins; D011980:Receptors, Progesterone; D011374:Progesterone