title: Isolation and characterisation of a progesterone- and testosterone-binding globulin from pregnant guinea pig serum.
abstract: A progesterone- and testosterone-binding globulin, has been isolated from a pool of pregnant guinea pig serum, using DEAE-Sephadex chromatography, gel filtration on Sephadex G-200 and preparative polyacrylamide gel electrophoresis. This globulin appeared to be heterogeneous on ion exchange chromatography, isoelectric focusing and equilibrium ultracentrifugation, indicating a quarternary structure sensitive to concentration and to ionic environment. In line with the steroid-binding serum proteins so far described progesterone-binding globulin is a glycoprotein with a carbohydrate content of 42%. Extrapolated sedimentation and diffusion coefficients were 4.52 S and 5.1.x 10(-7) cm2/s, respectively. A partial specific volume of 0.678 cm3/g has been calculated from the chemical composition. A molecular weight of 82,00 was obtained from equilibrium centrifugation experiments in the presence of o0I1 sodium dodecyl sulfate. The electrophloretic mobility at pH 8.6 corresponds to that of an a,lpha1globulin; isoelectric points were 4.4 and 3.5; Stokes radius, 4.9 nm; frictional ratio, 1.74; extinction coefficient at 280 nm, 7.3. Pure progesterone-binding globulin showed an association constant at 4.0 degrees of 14 x 10(9)M-(1) for progesterone. The affinity for testosterone was lower being 8.2 x 10(7) M(-1). The number of high-affinity binding sites was determined to 1.0 or both steroids.
authors.affiliation: Hormone laboratory, University of Bergen School of Medicine, 5000 Bergen, Norway.
authors.forename: O A
authors.initials: OA
authors.lastname: Lea
mesh_terms: D000818:Animals; D001665:Binding Sites; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005916:Globulins / Q000737:chemistry*; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007525:Isoelectric Focusing; D011247:Pregnancy; D011270:Pregnancy, Animal; D011374:Progesterone / Q000737:chemistry*; D011376:Progesterone-Binding Globulin / Q000737:chemistry*; D011485:Protein Binding; D012738:Sex Hormone-Binding Globulin / Q000737:chemistry*; D013256:Steroids / Q000737:chemistry; D013739:Testosterone / Q000737:chemistry*
chemical_list: D005916:Globulins; D007477:Ions; D011376:Progesterone-Binding Globulin; D012738:Sex Hormone-Binding Globulin; D013256:Steroids; D013739:Testosterone; D011374:Progesterone