Author/Editor		Lenasi, H
Title		Progesterone binding sites in the cytosol of filamentous fungi Rhizopus nigricans and Cochliobolus lunatus
Type		članek
Source		Acta Chim Slov
Vol. and No.		Letnik 42, št. 4
Publication year		1995
Volume		str. 419-24
Language		eng
Abstract		Filamentous fungi R. nigricans and C. lunatus contain a steroid hydroxylating system which could be effectively induced by progesterone and some other steroids (1, 2). To get an insight in this progesterone action we examined the cytosol of both fungi for the presence of progesterone binding proteins (PBP). To eliminate the influence of eventual endogenous compounds responsible for the basal enzyme activity on the experimental procedure for PBP detection, we treated the cytosol with dextran coated characoal (DCC) prior to progesterone binding assay. In this way two types of PBP were detected, one with higher affinity (R. nigricans - K/d1=3.0 nM; C. lunatus - K/d1 = 3.5 nM) and the other with lower affinity for progesterone (K/d2 could not be determined with accurancy because of the sigmoidal nature of the binding curve). The content of high affinity PBP varied in different experiments and reached maximal value in R. nigricans 218 fmol/mg protein and in C. lunatus 1045 fmol/mg protein. The susceptibility to hydrolytic enzymes and to heating revealed the protein nature of the binding molecules. The specificity of R. nigricans and C. lunatus PBP was relatively low except that effinity for progesterone was in both fungi significantly higher than for any other P450 inducing steroid. The presence of cytosolic PBP in R. nigricans and C. lunatus shown in this report suggests that PBP could represent part of P450 induction mechanism by steroids in these microorganisms; the precise role of two types of PBP is under investigation.
Descriptors		RHIZOPUS ASCOMYCETES PROGESTERONE BINDING SITES CYTOSOL HYDROXYLATION