The characterization of alpha-subunit of glycoprotein hormone produced by undifferentiated carcinoma.
The glycoprotein hormone alpha-subunit was extracted and purified from the urine of a patient with undifferentiated carcinoma producing isolated alpha-subunit. Its final specific immunoactivity was 0.92 (mg alpha-subunit/mg protein). The alpha-subunit exhibited virtually identical immunoantigenicity to hCG-alpha antiserum with standard hCG-alpha. The molecular weight of the alpha-subunit determined by gel chromatography on Sephadex G-100 was greater than that of standard hCG-alpha dissociated by urea in vitro. By SDS disc electrophoresis, however, the alpha-subunit moved faster than hCG-alpha separated by mercaptoethanol reduction. The amino acid composition of the alpha-subunit was quite similar to that of standard hCG-alpha. In the isoelectric focusing, the major components of the alpha-subunit from undifferentiated carcinoma and the alpha-subunit from urine of normal pregnant women (third trimester) were distributed over the range from pH 3.5 to 6.0, while standard hCG-alpha was distributed in the fractions ranging from pH 6.0 to 8.0. The result of a combination study in vitro indicated that both alpha-subunits from undifferentiated carcinoma and from urine of normal pregnant women did not actively combine with hCG-beta. These results suggest that the alpha-subunit secreted by undifferentiated carcinoma is virtually identical with standard hCG-alpha as the protein moiety but differs in regard to carbohydrate moiety, and also suggest that the excess of alpha-subunit, which is not associated with beta-subunit, may have undergone some intracellular modification, and consequently, the electric charge of the freely secreted alpha-subunit changes and it no longer has the ability to combine with the beta-subunit.
D000328:Adult; D000596:Amino Acids / Q000032:analysis; D002277:Carcinoma / Q000652:urine*; D006063:Chorionic Gonadotropin / Q000302:isolation & purification / Q000652:urine*; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004589:Electrophoresis, Disc; D005260:Female; D005266:Femoral Neoplasms / Q000652:urine; D015292:Glycoprotein Hormones, alpha Subunit; D006801:Humans; D007525:Isoelectric Focusing; D008175:Lung Neoplasms / Q000556:secondary; D010446:Peptide Fragments / Q000302:isolation & purification / Q000652:urine*; D011863:Radioimmunoassay
D000596:Amino Acids; D006063:Chorionic Gonadotropin; D015292:Glycoprotein Hormones, alpha Subunit; D010446:Peptide Fragments