Isolation and properties of the pituitary gonadotropin from silver carp (Hypophthalmichthys molitrix)

Purification of mummichog (Fundulus heteroclitus) gonadotropins and their subunits, using an immunochemical assay with antisera raised against synthetic peptides

To detect mummichog gonadotropins (GtHs) and their subunits immunochemically, fragment peptides with amino acid sequences corresponding to cDNA data were synthesized, and antisera were raised against them. In the case of GtH-IIbeta, large loops such as the second loop and the "seat belt" structure (deduced from the hCG 3D structural data) were considered to be favorable regions for antigen, although further examination is needed to determine if this is the case of GtH-Ibeta and GtH-alpha. In the purification process, glycoprotein was extracted from acetone-dried mummichog pituitary and separated by various liquid chromatography procedures. Each fraction was assayed by immunoblotting with the appropriate antisera against synthetic peptides. Subunits (GtH-alpha, GtH-Ibeta, and GtH-IIbeta) were obtained through gel filtration, anion-exchange chromatography, and reverse-phase HPLC. Intact bioactive GtH-I and GtH-II were obtained through gel filtration, anion-exchange chromatography, and hydrophobic chromatography. Both GtH-I and GtH-II dissociated into subunits under acidic conditions. Nominal MW of each subunit was estimated from SDS-PAGE as 23,000 for GtH-alpha from GtH-I, 22,000 for GtH-alpha from GtH-II, 18,000 for GtH-Ibeta, and 21,000 for GtH-IIbeta.

Isolation and characterization of two distinct gonadotropins from the pituitary gland of Mediterranean yellowtail, Seriola dumerilii (Risso, 1810)

Two gonadotropins, GTH I and GTH II, were isolated and chemically characterized from the pituitary of Mediterranean yellowtail. They were extracted with 35% ethanol-10% ammonium acetate, separated by ion-exchange chromatography on a DE-52 column, and purified by reversed-phase high-performance liquid chromatography on Asahipak C4P-50 and subsequently by gel filtration chromatography on Superdex 75. The molecular weights were estimated at 47 kDa for GTH I and 29 kDa for GTH II by SDS-PAGE and at 49 kDa for GTH I and 42 kDa for GTH II by gel filtration. GTH II was completely dissociated, while GTH I was partially dissociated into alpha- and beta-subunits by treatment with 0.1% trifluoroacetic acid. The complete amino acid sequences of GTH alpha-, GTH I beta-, and GTH II beta-subunits were determined. The GTH alpha-subunit consisted of 91 amino acid residues. The GTH I beta and GTH II beta consisted of 105 and 115 amino acid residues, respectively, and had a 28% sequence identity to each other. They had the highest sequence identity with the respective gonadotropin subunits of bonito, tuna, and striped bass: 81-83% for GTH alpha, 67-71% for GTH I beta, and 91-93% for GTH II beta. The sequence identity of the GTH alpha-subunit with those of other teleosts and human and bovine LH and FSH was 57-67%. The GTH I beta-subunit showed a low sequence identity with other known fish GTH I beta s (36-51%) and was more similar to human and bovine FSH beta s (34% identity) than to human and bovine LH beta s (29% identity). The sequence identity of the GTH II beta-subunit with those of other teleosts was higher (60-73%), being more similar to LH beta s (43% identity) than FSH beta s (38% identity). Thus, two distinct gonadotropins, GTH I and GTH II, homologous to mammalian FSH and LH, respectively, are synthetized by M. yellowtail pituitary glands.

Purification, characterization, and molecular cloning of gonadotropin subunits of silver carp (Hypophthalmichthys molitrix)

The alpha and beta subunit of silver carp gonadotropin (scGTH-alpha and scGTH-beta) were isolated by high-performance liquid chromatography. Heterogeneity of N-terminal amino acid sequence was observed in scGTH-alpha but not in scGTH-beta. For determining the complete primary structures of scGTH-alpha and scGTH-beta, their cDNAs were cloned. Combining the data of N- and C-terminal sequences determined from proteins and the amino acid sequences deduced from cDNAs, we infer that scGTH-alpha consists of 95 and/or 93 residues and scGTH-beta consists of 115 residues. Both scGTH-alpha and scGTH-beta are glycoprotein. Their carbohydrate content is about 20 g per 100 g protein. The molecular weights of scGTH-alpha and scGTH-beta were calculated to be 12,700 and 15,700 Da, respectively. The amino acid sequences of scGTH-alpha and scGTH-beta are very similar to those of the corresponding subunit of carp GTH, different in only 2 and 4 residues, respectively. In addition, a high extent of homology (70%) was also observed between the alpha subunits of fish and mammalian GTHs. In the case of beta subunit, homology among various species of fish (75 to 98%) is much higher than that between fish and mammal (40%). These data suggest that the alpha subunit is conserved while the beta subunit is diversified during the molecular evolution of vertebrate GTH.

Primary structures of carp gonadotropin subunits deduced from cDNA nucleotide sequences

The alpha and beta subunits of carp gonadotropin (cGTH) were isolated by high performance liquid chromatography. They were identified to be the subunits of cGTH by bioassay and by partial N-terminal amino acid sequence analysis. To elucidate the complete primary structures of the alpha and beta subunits of cGTH, cDNA cloning technique was employed. The alpha and beta subunits consist of 95 and 115 amino acid residues, respectively. Homology of the alpha subunit of cGTH to those of mammalian GTH is around 70%. In comparison, the extent of homology of the beta subunit between carp and salmon GTH (75%) is higher than that between fish and mammalian GTH (39-47%). Such comparative data suggest that the alpha subunit is highly conserved while the beta subunit is diversified during the molecular evolution of vertebrate GTH.