Membrane Progestin Receptor Gamma (MPRg)

The deduced proteins contain about 330 amino acids, consisting of an extracellular N terminus, an intracellular C terminus, and 7 transmembrane domains. Northern blot analysis detected a 5.8-kb transcript expressed at high levels only in kidney. RNA dot blot analysis detected highest expression in adult and fetal kidney, colon, lung carcinoma, and HeLa cells, and showed possible expression in adrenal gland and normal lung.

MPRG, expressed by E. coli, showed high-affinity progesterone binding. Steroid competition studies showed specific binding to progesterone and several of its hydroxylated derivatives, whereas estrogen, androgen, and corticosteroid had low or no affinity for the receptor. Association and dissociation kinetics were rapid.