Heterogeneity of free alpha-subunit in term placenta.

Free alpha-subunit in normal term placenta was examined for molecular weight, electric charge and ability to combine with standard hCG-beta in comparison with extracellular free alpha-subunit and standard hCG-alpha dissociated from urinary hCG in vitro. The gel chromatography on Sephadex G-100 of the placental extract revealed three major immunoreactive hCG-alpha peaks, designated as P alpha-A (Kav = 0.32-0.46), P alpha-B (0.47-0.58) and P alpha-C (0.59-0.70), near the position of standard hCG-alpha. In the isoelectric focusing, while P alpha-A was mainly distributed over the acidic region, the major components of P alpha-B and P alpha-C were distributed over the basic region. Furthermore, in the combination study with standard hCG-beta, such a alpha-subunit with acidic pI scarcely showed any combining activity whereas alpha-subunit with basic pI revealed significant combining activity. These results suggest the following possibilities: that 1) the various size species of placental alpha-subunit may be responsible for the progressive glycosylation; 2) the small alpha-subunit with basic pI may combine with beta-subunit to form immunoreactive hCG; 3) the alpha-subunit, which has not associated with beta-subunit, may be converted to a large and incombinative form with acidic pI by further glycosylation, followed by secretion as a free alpha-subunit.

[1]  R. Canfield,et al.  Biological and immunological characterization of crude commercial human choriogonadotropin. , 1982, The Journal of clinical endocrinology and metabolism.

[2]  T. Hamamoto,et al.  The characterization of alpha-subunit of glycoprotein hormone produced by undifferentiated carcinoma. , 1982, Endocrinologia japonica.

[3]  R. Nishimura,et al.  The biochemical properties of urinary human chorionic gonadotropin from the patients with trophoblastic diseases , 1981, Journal of endocrinological investigation.

[4]  A. Chrambach,et al.  Physical, biological, and immunological characterization of highly purified urinary human chorionic gonadotropin components separated by gel electrofocusing. , 1981, Endocrinology.

[5]  M. Oermann,et al.  [Clinical evaluation]. , 1981, Ugeskrift for laeger.

[6]  R. Shownkeen,et al.  Physicochemical and immunological characterization of an HCG-like substance from human pituitary glands , 1980, Nature.

[7]  B. Weintraub,et al.  Relationship of glycosylation to de novo thyroid-stimulating hormone biosynthesis and secretion by mouse pituitary tumor cells. , 1980, The Journal of biological chemistry.

[8]  B. Weintraub,et al.  Increased glycosylation of serum human chorionic gonadotropin and subunits from eutopic and ectopic sources: comparison with placental and urinary forms. , 1980, The Journal of clinical endocrinology and metabolism.

[9]  B. Weintraub,et al.  De novo synthesis and secretion of heterogeneous forms of human chorionic gonadotropin and its free alpha-subunit in the human choriocarcinoma clonal cell line JEG-3. , 1980, Endocrinology.

[10]  R. Nishimura,et al.  The clinical evaluation of the simultaneous measurements of human chorionic gonadotropin (hCG) and its alpha-subunit in sera of patients with trophoblastic diseases. , 1979, Endocrinologia japonica.

[11]  J. Lindner,et al.  Human Chorionic Gonadotropin α-Subunit from Cultured Choriocarcinoma (JEG) Cells: Comparison of the Subunit Secreted Free with That Prepared from Secreted Human Chorionic Gonadotropin , 1979 .

[12]  G. A. Grant,et al.  Processing of placental peptide hormones synthesized in lysates containing membranes derived from tunicamycin-treated ascites tumor cells. , 1978, The Journal of biological chemistry.

[13]  S. Daniels-McQueen,et al.  Identification of mRNAs encoding the alpha and beta subunits of human choriogonadotropin. , 1978, The Journal of biological chemistry.

[14]  M. Bielińska,et al.  mRNA-dependent synthesis of a glycosylated subunit of human chorionic gonadotropin in cell-free extracts derived from ascites tumor cells. , 1978, Proceedings of the National Academy of Sciences of the United States of America.

[15]  J. Vaitukaitis.  Glycoprotein Hormones and Their Subunits—Immunological and Biological Characterization , 1978 .

[16]  B. Weintraub,et al.  Combination of ectopic and standard human glycoprotein hormone alpha with beta subunits: discordance of immunologic and receptor-binding activity. , 1977, Endocrinology.

[17]  R. Hussa.  Immunologic and physical characterization of human chorionic gonadotropin and its subunits in cultures of human malignant trophoblast. , 1977, The Journal of clinical endocrinology and metabolism.

[18]  S. Boguslawski,et al.  The cell-free synthesis of the alpha subunit of human chorionic gonadotropin. , 1976, Endocrinology.

[19]  B. Weintraub,et al.  Differences between purified ectopic and normal alpha subnits of human glycoprotein hormones. , 1975, The Journal of clinical investigation.

[20]  T. Muramatsu,et al.  Fractionation of glycopeptides by affinity column chromatography on concanavalin A-sepharose. , 1975, Journal of biochemistry.

[21]  C. K. Cain,et al.  THE PREPARATION OF CHORIONIC GONADOTROPIN BY CHROMATOGRAPHIC ADSORPTION , 1943 .