Existence of associated, non-associated, and oligomeric forms of human chorionic gonadotropin subunits in placental extracts.
The molecular sizes of human chorionic gonadotropin (hCG) subunits in the native state in normal first trimester placental extracts were determined by gel filtration on Sephacryl S-300, followed by SDS-polyacrylamide gel electrophoresis, protein blotting, and immunobinding analysis using anti-alpha and - beta antibodies. Mature forms of hCG subunits in the extracts were only found in the same fraction as that which contained standard urinary hCG, indicating an alpha beta dimer. On the other hand, immature forms were detected with a wide range of molecular weights, which were higher than that of standard hCG, suggesting oligomerization of associated or non-associated immature subunits. In order to determine the associated state of these subunits, various forms of associated subunits (hCG alpha beta) in placental extracts were immunoprecipitated with anti-hCG antiserum, which only recognized hCG alpha beta, and Protein A-Sepharose. They were then analyzed by SDS-polyacrylamide gel electrophoresis under reducing and non-reducing conditions, followed by immunobinding assaying. It has been suggested that there are three kinds of hCG alpha beta S (one mature and two immature). To confirm the above results and to clarify the existence of free subunits, placental extracts were subjected to two-dimensional SDS-polyacrylamide gel electrophoresis. With this technique, high molecular weight forms of immature hCG subunits were found to be present in placental cells as an oligomer of not only the alpha beta dimer but of each subunit as well.
Department of Biochemistry, School of Clinical Pharmaceutical Sciences, Nagasaki University.
N
N
Tominaga
R
R
Sakakibara
Y
Y
Yokoo
M
M
Ishiguro
D006063:Chorionic Gonadotropin / Q000032:analysis* / Q000652:urine; D002850:Chromatography, Gel; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D006801:Humans; D009439:Neuraminidase; D010920:Placenta / Q000032:analysis*; D011233:Precipitin Tests; D011247:Pregnancy; D014020:Tissue Extracts / Q000032:analysis*
D006063:Chorionic Gonadotropin; D014020:Tissue Extracts; D009439:Neuraminidase