The apparent molecular weight of androgen-binding protein (ABP) in the blood of immature rats differs from that of ABP in the epididymis.
When androgen-binding protein (ABP) in unfractionated immature (20-day old) male rat serum was covalently labeled with the site-specific photoaffinity ligand [3H]17 beta-hydroxy-4,6-androstadien-3-one and analyzed on 5.6% polyacrylamide tube gels containing SDS (SDS-PAGE), a protein of Mr 33,700 +/- 1200 was shown to be specifically labeled. Rat epididymal ABP from unfractionated cytosol analyzed under identical conditions exhibited two androgen-specific peaks of radioactivity, Mr 49,900 +/- 600 and Mr 44,100 +/- 800, which correspond to the previously described subunits of ABP. The apparent molecular weight differences between serum and epididymal ABP were further assessed on preparations of serum ABP that had been partially purified by chromatography on Affi-Gel blue (to remove albumin) and on Sephadex G-150 (to remove other proteins). When these preparations of ABP were photolabeled and analyzed by SDS-PAGE as above, two subunits of Mr 61,700 +/- 1300 and Mr 47,100 +/- 700 were resolved. Serum and epididymal ABP were further purified by androgen affinity chromatography. When these preparations were subjected to SDS-PAGE on slab gels containing 10% polyacrylamide and identified by fluorography of photolabeled ABP or by immunochemical localization following electrophoretic transfer to nitrocellulose, differences in the apparent molecular weight of ABP from the two sources persisted. Immunochemical localization studies on ABPs that had been desialylated with neuraminidase indicated that there was an increased mobility of the subunits, as one would anticipate from removal of carbohydrate. Differences in apparent molecular weight of ABPs from the two sources are likely due to differences in glycosylation.
Danzo
B J
BJ
Department of Obstetrics and Gynecology, Vanderbilt University School of Medicine, Nashville, TN 37232.
Eller
B C
BC
Bell
B W
BW
D000345:Affinity Labels; D000727:Androgen-Binding Protein / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D002845:Chromatography; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004822:Epididymis / Q000378:metabolism*; D006031:Glycosylation; D007118:Immunoassay; D008297:Male; D008970:Molecular Weight; D009439:Neuraminidase / Q000494:pharmacology; D010777:Photochemistry; D051381:Rats; D011919:Rats, Inbred Strains; D013739:Testosterone / Q000031:analogs & derivatives / Q000378:metabolism
D000345:Affinity Labels; D000727:Androgen-Binding Protein; C023630:6-dehydrotestosterone; D013739:Testosterone; D009439:Neuraminidase