PARTIAL CHARACTERIZATION AND QUANTITATION OF A HUMAN PROSTATIC ESTRAMUSTINE-BINDING PROTEIN

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (5) , 1935-1942
Abstract
The [3H]estramustine-binding macromolecule in human prostate was partially characterized. Although human estramustine-binding protein (HEMBP) tended to aggregate in several systems, a MW of .apprx. 54,000 was determined by gel filtration on Sephacryl S-200 Superfine and high-performance liquid chromatography. A sedimentation-coefficient of .apprx. 3.6S was obtained for HEMBP by sucrose density gradient centrifugation. Isoelectric focusing in polyacrylamide gels indicated an isoelectric point of 4.7-4.8, which was in agreement with the elution position of HEMBP following chromatofocusing on Polybuffer Exchanger 94. HEMBP was eluted from diethylaminoethyl-Sepharose with 0.23 MKCl, was retained by concanavalin A-Sepharose (indicating that HEMBP is a glycoprotein), but did not interact with Affi-Gel Blue. Separation between the [3H]estramustine-labeled HEMBP and the [3H]estramustine-human serum albumin complex was obtained on sucrose density gradients by chromatography on Affi-Gel Blue, by chromatofocusing, by gel filtration, by isoelectric focusing, and on concanavalin A-Sepharose by affinity chromatography. Of 27 human benign hyperplastic prostate cytosol samples, 22 contained protein immunochemically similar to estramustine-binding protein (EMBP) purified from rat ventral prostate as determined by EMBP radioimmunoassay. Concentrations from 0.2 to 139.6 ng EMBP per mg of total cytosolic protein (mean, 19.3) were determined. Four of 7 prostatic cancer specimens contained rat EMBP-immunoreactive material. The concentration of HEMBP in the carcinomatous tissue may be of significance in determining the uptake of estramustine phosphate (Estracyt) in carcinoma tissue.