[Isolation and characterization of a high molecular weight placental protein (PPg)(author's transl)].

The isolation and characterization of a high molecular weight protein (PP6) from human placentae is described. The protein which apparently has some steroid-binding properties shows the mobility of an alpha1-globulin and has a molecular weight of around 1 X 10(6) daltons. The molecule is composed of several different subunits with molecular weights ranging from 200,000-35,000 daltons which are held together by non-covalent bonds. Immunofluorescent studies revealed that the placental protein PP6 is localized in the nuclei of the syncytiotrophoblast. But PP6 is not specific for the placenta; this protein is also found in extracts from other human tissues as well as in the erythrocytes. PP6 usually is not present in normal sera but in some cases it could be detected in concentrations ranging from 1-3 mg per 100 ml in sera from pregnant women and in sera from patients with malignant tumors.