Purification of androgen-binding protein from rat testis using high-performance liquid chromatography and physicochemical properties of the iodinated molecule

The androgen-binding protein (ABP) has been purified 87 500-fold from rat testis using 4 steps of HPLC, with a yield of 14%. The molecule was 99% pure with a specific activity estimated to 16 600 pmol/mg protein. The iodinated molecule was eluted in 2 peaks in Sephacryl S300 gel filtration with a molecular mass estimated to be 92 600 ± 3300 and 50 300 ± 4000 Da. The column isoelectrofocusing of 125I-ABP demonstrated 3 isoproteins isoelectric at pH 4.7, 4.9 and 5.3 and the sedimentation coefficient was estimated to be 4.7 S in sucrose gradient ultracentrifugation. The 125I-ABP had similar physicochemical properties to the non-labelled ABP of epididymis.