Avtor/Urednik		Lenasi, Helena; Bavec, Aljoša; Zorko, Matjaž
Naslov		Membrane-bound progesterone receptors coupled to G proteins in the fungus Rhizopus nigricans
Tip		članek
Vir		Fems Microbiol Lett
Vol. in št.		Letnik 213
Leto izdaje		2002
Obseg		str. 97-101
Jezik		eng
Abstrakt		Steroid binding sites with high affinity for progesterone (Kd = 40 +- 14 nM determined by binding, and Kd = 71 +- 22 nM determined by displacement studies) and lower affinity for 21-hydroxyprogesterone and for testosterone, but no affinity for estradiol-17beta, onapristone and a-naphthoflavone were detected in the enriched plasma membrane fraction of the fungus Rhizopus nigricans. The amount of steroid binding sites is in accordance with the value of Bmax = 744 +- 151 fmol (mg protein)-1. In the membrane fraction, progesterone induced about 30% activation of G proteins over basal level, as determined by GTPase activity (EC50 = 32 +- 8 nM) and by the guanosine 5'-O-(3thiotriphosphate) (GTPyS) binding rate (EC50 = 61 +- 21 nM). The affinity of receptors for progesterone was substantially decreased in the presence of GTPdeltaS and of cholera toxin. Our results suggest the existence of progesterone receptors in the membrane of Rhizopus nigricans and their coupling to G proteins.
Deskriptorji		RHIZOPUS RECEPTORS, PROGESTERONE GTP-BINDING PROTEINS GTP PHOSPHOHYDROLASE BINDING SITES BINDING, COMPETITIVE TESTOSTERONE DESOXYCORTICOSTERONE GUANOSINE 5'-O-(3-THIOTRIPHOSPHATE)