Phenylmethylsulfonyl fluoride (PMSF) inhibits 17 beta-estradiol binding to estrogen receptor from human prostate

Estrogen receptor binding studies were performed on cytosol obtained from human benign prostatic hyperplasia (BPH) tissue. Binding assays were done in the absence or presence of various concentrations of phenylmethylsulfonyl fluoride (PMSF). Saturation analysis and Scatchard plots showed that the binding of 17 beta -estradiol to the estrogen receptor (ER) was inhibited by PMSF. The nature of the inhibition appears to be uncompetitive, as determined from double-reciprocal plots. Glycerol density gradient centrifugation analysis also confirmed the results obtained with Scatchard plots. The inhibition observed in the presence of dithiothreitol (DTT) was greater than the inhibition observed in the absence of DTT. The maximum number of binding sites (Bmax) observed in our present study was 59.1 +/- 34.1 fmol/mg protein with an equilibrium dissociation constant (KD) of 2.2 +/- 2.2 nM. Our study indicates that PMSF significantly affects 17 beta -estradiol binding to ER and consequently alters the estimation of ER in Human BPH.