Effective separation of human chorionic gonadotropin subunits by high performance gel permeation chromatography

Human chorionic gonadotropin (hCG) was effectively separated into alpha and beta subunits by treating with 8 M guanidine hydrochloride, followed by high performance gel permeation chromatography (GPC) on a 2.5 X 60 cm TSK G 3000 SW column in 6 M guanidine hydrochloride. Their molecular weights estimated by GPC were about 29,000 daltons for the beta subunit and 19,000 daltons for the alpha subunit. Both subunits were examined for SDS-polyacrylamide gel electrophoresis, amino acid analyses and radioimmunoassay, respectively. Neither subunit showed significant binding to the hCG-receptor fraction of rat Leydig cell in vitro. However, the separated subunits easily recombined and recovered about 90% of receptor binding activity of intact hCG. The present results indicate that the GPC technique is an effective, simple and non-denaturing method for the separation of hCG into alpha and beta subunits.