PURIFICATION AND CHARACTERIZATION OF THE CORTICOSTEROID-BINDING GLOBULIN OF PREGNANT GUINEA-PIG SERUM

The corticosteroid-binding globulin from guinea pig pregnancy serum was purified by the sequential use of affinity chromatography, hydroxylapatite chromatography and gel filtration chromatography at a cumulative yield of 80%. The protein was found to be homogeneous by analytical gel electrophoresis, equilibrium sedimentation ultracentrifugation, immunoelectrophoresis and stoichiometry (1:1) of steroid binding. Guinea pig corticosteroid-binding globulin has a molecular weight of 43 300 and contains 29% carbohydrate. The intrinsic fluorescence of the corticosteroid-binding globulin is quenched by about 73% when 1 mol of Cortisol is bound. The association constants (pH 7.4) at 4 and 37 °C are 2.5 × 107 and 1.5 × 106 M-1 for Cortisol and 1.4 × 106 and 0.2 × 106 M-1 for progesterone, respectively. © 1979, American Chemical Society. All rights reserved.