Pike eel (Muraenesox cinereus) gonadotropin. Amino acid sequences of both alpha and beta subunits

Isolation of the pituitary gonadotrophic α-subunit hormone of the giant amazonian fish: pirarucu (Arapaima gigas)

The cDNAs of the α-subunit of the pituitary gonadotrophic hormones (GTHα) of fish of the order Osteoglossiformes or the superorder Osteoglossomorpha have never been sequenced. For a better understanding the phylogenetic diversity and evolution of PGHα in fish and for future biotechnological synthesis of the gonadotrophic hormones (ag-FSH and ag-LH), of Arapaima gigas, one of the largest freshwater fishes of the world, its GTHα cDNA was synthesized by reverse transcriptase and the polymerase chain reaction starting from total pituitary RNA. The ag-GTHα-subunit was found to be encoded by 348 bp, corresponding to a protein of 115 amino acids, with a putative signal peptide of 24 amino acids and a mature peptide of 91 amino acids. Ten cysteine residues, responsible for forming 5 disulfide linkages, 2 putative N-linked glycosylation sites and 3 proline residues, were found to be conserved on the basis of the known sequences of vertebrate gonadotrophic hormones. Phylogenetic analysis, based on the amino acid sequences of 38 GTHα-subunits, revealed the highest identity of A. gigas with members of the Acipenseriformes, Anguilliformes, Siluriformes and Cypriniformes (87.1-89.5 %) and the lowest with Gadiformes and Cyprinodontiformes (55.0 %). The obtained phylogenetic tree agrees with previous analysis of teleostei, since A. gigas, of the order of Osteoglossiformes, appears as the sister group of Clupeocephala, while Elopomorpha forms the most basal group of all other teleosts.

Cloning of complimentary deoxyribonucleic acid encoding follicle-stimulating hormone and luteinizing hormone beta subunit precursor molecules in Reeves's turtle (Geoclemys reevesii) and Japanese grass lizard (Takydromus tachydromoides)

Reptilia is the only vertebrate class in which cDNA for the gonadotropin beta subunit precursor molecule has not been cloned. We have isolated the full-length cDNA clone encoding the LH beta subunit precursor molecule and a partial cDNA clone encoding the FSH beta subunit precursor molecule from a pituitary cDNA library of Reeves's turtle. We further clarified the nucleotide sequence of the remaining part of the turtle FSH beta cDNA and that of full-length cDNA encoding the LH beta subunit precursor molecule of the Japanese grass lizard, by means of the 5' rapid amplification of cDNA end (RACE) and 3' RACE. The nucleotide sequence of the turtle FSH beta cDNA we determined was 584 bp long and contained the coding sequence, 5' untranslated region (UTR) and 3' UTR of 396, 34, and 154 bp, respectively. The nucleotide sequence of the turtle LH beta we isolated was 498 bp long and contained the coding sequence, 5' UTR and 3' UTR of 420, 7, and 71 bp, respectively. The nucleotide sequence of the lizard LH beta we determined was 537 bp long and contained the coding sequence, 5' UTR and 3' UTR of 441, 35, and 61 bp, respectively. Amino acid sequences deduced from coding regions of the turtle FSH beta, LH beta and the lizard LH beta were 131, 139, and 146 residues, respectively. Referring to the amino acid sequences of the bullfrog FSH and LH beta subunit molecules determined chemically, we deduced the amino acid sequences of mature peptide. Amino acid sequences of mature peptides of the turtle FSH, turtle LH, and the lizard LH were 111, 112, and 112 residues, respectively. Amino acid sequences of the mature peptides were compared with those of other vertebrates. The amino acid sequence of the turtle FSH beta subunit molecule was 84.7-85.6, 67.8-71.4, and 61.3-62.2% identical to the FSH sequence of birds, mammals, and amphibians, respectively. The amino acid sequence of the turtle LH beta subunit molecule was 51.6-54.6, 36.2-48.7, and 56.3-57.5% identical to the LH sequence of birds, mammals, and amphibians, respectively. The amino acid sequence of the lizard LH beta subunit molecule was 39.1-47.1, 32.9-43.0, and 46.0-47.3% identical to the LH sequence of birds, mammals, and amphibians, respectively. These identity values suggest that the turtle or reptilian FSH beta subunit molecule is more closely related to avian and mammalian FSH beta subunit molecules than to amphibian FSH beta subunit molecules but reptilian LH beta subunit molecules are more closely related to amphibian LH beta subunit molecules than to avian and mammalian LH beta subunit molecules. This discrepancy in the molecular similarity relationship found in the reptilian FSH and LH beta subunit molecules can be interpreted by assuming that evolution speed was not the same among hormone species and also among vertebrate groups.

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.

Studies on the structure and function of the carp gonadotropin alpha subunit by site-directed mutagenesis

There are two genes encoding the alpha subunit of carp gonadotropin (alpha 1 and alpha 2 subunits). Our previous data have demonstrated that both alpha 1 and alpha 2 subunits expressed in insect cells are able to associate with the beta subunit, but only the alpha 1/beta heterodimer displays biological activity. In the mature protein, there are only four amino-acid residues different between the alpha 1 and alpha 2 subunits. In this study we used site-directed mutagenesis and expressed different mutant alpha subunits in insect cells to identify which residue might be important for biological activity of the alpha subunit. Our results suggested that the change of Arg-71 to Gln-71 affected the activity of the carp gonadotropin alpha subunit.

Purification and characterization of gonadotropin I and II from pituitary glands of tuna (Thunnus obesus)

The duality of teleost pituitary gonadotropins was established in an advanced marine fish, the tuna (Thunnus obesus). Two different molecular forms of gonadotropins, designated tGTH I and tGTH II, were isolated from an alcoholic extract of pituitary glands following ion-exchange chromatography and reversed-phase HPLC. Both tGTH I and tGTH II stimulated estradiol-17 beta and testosterone production in tuna ovarian follicles in vitro, although responses to tGTH II were significantly greater than those to tGTH I. Each gonadotropin consisted of alpha- and beta-subunits. tGTH I was stable in acidic conditions, whereas tGTH II dissociated into two subunits after acid treatment. Alpha subunits of tGTH I and tGTH II had identical amino acid sequences of 94 amino acid residues. The tGTH I beta and tGTH II beta consisted of 102 and 115 amino acid residues, respectively, and showed 35% sequence identity. tGTH I beta is structurally more similar to salmon GTH I beta than to salmon GTH II beta, whereas tGTH II beta is more similar to salmon GTH II beta. Thus it is evident that the tuna pituitary gland produces two chemically distinct gonadotropins.

Molecular structures of glycoprotein hormones and functions of their carbohydrate components

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The complete amino acid sequence of the follitropin beta-subunit of the bullfrog, Rana catesbeiana

The amino acid sequence of the bullfrog, Rana catesbeiana, follitropin beta-subunit has been determined by sequencing the intact protein (residues 1-39) and peptides originated by lysyl endopeptidase and pepsin. Twelve cysteine residues and two sugar chain binding sites at Asn-5 and Asn-22 are positional identities with bullfrog and mammalian beta-subunits. The bullfrog FSH beta-subunit is composed of 107 amino acid residues with a molecular mass of 11,782 Da, including the six cystine bridges and excepting the sugar chain. The bullfrog FSH beta-subunit has approximately 60% sequence identity with that of mammals and 40% with the fish gonadotropin beta-subunit. Conserved sequences among mammals (residue numbers 33-55 and 66-71) extensively differed from those of the bullfrog.

The primary structures of growth hormones of three cyprinid species: bighead carp, silver carp, and grass carp

The primary structures of growth hormone (GH) of three cyprinid species, bighead carp, silver carp, and grass carp, were determined by a chemical method and/or by molecular cloning. The bighead carp GH was extracted from pituitary tissue by use of an alkaline medium, then successively purified by gel filtration, hydrophobic interaction column chromatography, and reverse-phase high-pressure liquid chromatography. The primary structure of bighead carp GH determined chemically is identical to that deduced from the cDNA nucleotide sequence. By molecular cloning, the primary structures of silver carp and grass carp GHs were also determined. The GHs of these three cyprinid species all contain 188 amino acid residues and their sequences are identical. When four of the five cysteines of cyprinid GHs were arranged to match the same positions of cysteines of other vertebrate GHs, a maximally matched alignment was achieved. Among fishes, GHs are relatively conserved within the same order (82 to 100% identity) but they are more diversified between orders (49 to 68% identity). In further comparison, fish GHs are even more different from tetrapod GHs (37 to 58% identity). Although the primary structures of vertebrate GHs are relatively variable, four homologous sequences, notably one located at the C-terminal, are found.

Fundulus heteroclitus gonadotropins. 3. Cloning and sequencing of gonadotropic hormone (GTH) I and II beta-subunits using the polymerase chain reaction

mRNA was isolated from Fundulus heteroclitus pituitaries and used to construct a cDNA library in lambda gt22A. A series of synthetic oligonucleotides, based on conserved regions of teleost gonadotropic hormone (GTH) beta-subunits, were constructed and used as primers in the polymerase chain reaction (PCR) to amplify GTH cDNAs. Appropriate length PCR products were subcloned and sequenced. Eight clones were eventually identified as cDNAs encoding two distinct beta-subunits of F. heteroclitus, GTH I and GTH II. By comparison with known GTH sequences, putative signal sequences of 19 end 21 amino acids and mature beta-subunits of 95 and 115 amino acids were found for GTH I and GTH II, respectively. Both beta-subunits had well conserved cysteine positions when aligned with other members of the glycoprotein family. The elucidation of the complete nucleotide sequences of two types of F. heteroclitus GTH provides definitive proof that in this species there are at least two distinct forms of pituitary GTH analogous to the classical luteinizing hormone-follicle stimulating hormone family.

Amphibian lutropin from the bullfrog Rana catesbeiana. Complete amino acid sequence of the beta subunit

The amino acid sequence of lutropin (LH) beta subunit of an amphibian, the bullfrog Rana catesbeiana, has been determined. The primary structure was determined by sequencing the intact protein (residues 1-44) and peptides originated by cyanogen bromide cleavage and lysyl endopeptidase digestion. 12 cysteine residues are conserved in the bullfrog and mammalian LH beta subunit. One sugar-chain-binding site at Asn-8 is also conserved in the bullfrog and in all mammals except humans. This glycoprotein is composed of 112 amino acid residues with a molecular mass of 12675 Da, considering the six cystine bridges and excepting the sugar chain. The bullfrog beta subunit has approximately 50% sequence identity with that of mammals and with the fish gonadotropin beta subunit, and about 40% with bullfrog follicle-stimulating hormone beta subunit.

Amphibian lutropin and follitropin from the bullfrog Rana catesbeiana. Complete amino acid sequence of the alpha subunit

The amino acid sequence of the alpha-subunit of the gonadotropins, lutropin and follitropin from bullfrog, Rana catesbeiana, has been determined. The alpha-subunit was identified in both hormones by the amino acid composition and ovulation activity of lutropin in the Xenopus ovary, by means of reconstituted hormones in various combinations. The amino acid sequences of two identical alpha-subunits from lutropin and follitropin were determined or deduced by different strategies. The alpha-subunit of those gonadotropins have 97 amino acid residues, the longest among the known alpha-subunits of gonadotropins, and one arginine insertion at position 29. Ten cysteine residues and two sugar-chain binding sites at Asn57 and Asn83 are completely conserved among the species. The molecular mass of this subunit is 11,026 Da not including the sugar chains. The bullfrog alpha-subunit has approximately 70% sequence identity with mammalian alpha-subunits.

Organization and nucleotide sequence of carp gonadotropin α subunit genes

We have used PCR to amplify and align the sequence of two genes encoding cGTH alpha. Both genes comprise four exons and three introns. The organization of cGTH alpha genes is very similar to that of mammalian GTH alpha genes. However, the cGTH alpha genes only span a region of 1.2 kb which is much smaller than those mammalian GTH alpha genes.

Expression of two forms of carp gonadotropin alpha subunit in insect cells by recombinant baculovirus

There are two types of cDNA clones (designated alpha 1 and alpha 2) encoding the alpha subunit of carp gonadotropin. These two cDNAs are derived from different genes and encode proteins that differ by seven amino acid residues (three in the signal peptide and four in the mature polypeptide). Expression of these two cDNAs in insect cells by recombinant baculovirus revealed that the alpha 1 subunit, after noncovalent association with the beta subunit, has the same potency as the native alpha subunit purified from the pituitary. In contrast, the alpha 2 subunit can associate with the beta subunit, but only to form an inactive gonadotropin. Competition of the alpha 2 subunit with the alpha 1 subunit for association with the beta subunit decreases the gonadotropin activity of the alpha/beta complex. In addition, both alpha 1 and alpha 2 subunits are secreted into the culture medium by insect cells and have an apparent molecular mass approximately 5 kDa higher than that of the native alpha subunit. These results indicate that the insect cell-derived alpha 1 subunit is biologically active and that those four amino acid changes in the mature of alpha 2 protein affect the biological activity and thus provide valuable clues for the study of the structure-function relationship of the alpha subunit of glycoprotein hormones.

Cloning and sequence analysis of the cDNA for the pituitary glycoprotein hormone alpha-subunit of the European eel

A cDNA library constructed using mRNAs isolated from pituitary glands of estradiol-treated eels was screened with a cDNA fragment for the rat glycoprotein hormone alpha-subunit. Three out of 10,000 cDNA clones were revealed and subcloned in pUC13 for characterization and sequencing. All three had the same nucleotide sequence except for a single, silent change in the coding sequence for one of them, and for the location of the poly(A) tail. Analysis of the deduced amino acid sequence strongly suggests that these cDNA clones encode the precursor for the eel common glycoprotein hormone alpha-subunit. This precursor would therefore consist of a 93 amino acid apoprotein preceded by a 24 amino acid long signal peptide. Alignment with glycoprotein hormone alpha-subunits from fish and mammals reveals high homology, ranging from 60 to 90%. Particularly, the ten cysteines and the two putative N-linked glycosylation sites were at the same position. Comparison between fish and mammals shows also that two regions are highly conserved, comprising about half of the protein length. This high conservation rate through evolution argues for the importance of these regions in the conservation of biological properties of the alpha-subunits. In contrast, other regions are highly variable and could be responsible for the immunological specificity. Northern blot analysis of pituitary RNA from control and estradiol-treated eels showed that estradiol treatment strongly increases the pituitary content of mRNA encoding the glycoprotein hormone alpha-subunit.