Author/Editor		Lenasi, H; Plemenitaš, A; Hudnik-Plevnik, T
Title		Progesterone binding sites in the plasma membrane of filamentous fungi Rhizopus nigricans and Cochliobolus lunatus
Type		članek
Source		Farm Vestn
Vol. and No.		Letnik 47, št. 2
Publication year		1996
Volume		str. 199-203
Language		eng
Abstract		It is known that filamentous fungi R. nigricans and C. lunatus are capable to transform steroids by enzymes which could be induced by different inducers (1,2). This induction proces could be mediated through specific progesterone binding sites in the plasma membrane, the first site of contact to environmental changes. In the present communication we examined plasma membrane fraction of fungi R. nigricans and C. lunatus for the presence of the progesterone receptors. Competitive binding assay was used as experimental technique and results analysed according to Scatchard. In both microorganisms specific membrane binding sites were detected. In C. lunatus the single type of binding site with Kd 13,9 nM and Bmax 260 fmol/mg protein was identified whereas in R. nigricans two types of binding sites were detected (Kd2=4nM and Kd2=21 nM; Bmax2=63 and Bmax2=348 fmol/mg protein). All binding molecules were heat labile and sensitive to proteinase treatment which confirm the proteinous nature of the receptors. The specificity of membraneous binding proteins was tested by displacement studies; in both fungi progesterone could be effectively displaced by 210H-progesterone and testosterone and less effectively by estrogens (E, and E2). The displacement ability of different competitors was in correlation with their capability to induce steroid transforming enzymes (3) which could indicate the involvement of progesterone receptors in the induction process.
Descriptors		RHIZOPUS ASCOMYCETES RECEPTORS, PROGESTERONE BINDING SITES CELL MEMBRANE