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Larson SB, McPherson A. The crystal structure of the β subunit of luteinizing hormone and a model for the intact hormone. Curr Res Struct Biol 2019; 1:1-5. [PMID: 34235462 PMCID: PMC8244496 DOI: 10.1016/j.crstbi.2019.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 07/22/2019] [Accepted: 07/31/2019] [Indexed: 11/24/2022] Open
Abstract
The β subunit of bovine luteinizing hormone (LH) was crystallized and its structure solved to 3.15 Å resolution by molecular replacement using human chorionic gonadotropin (hCG) β subunit as search model. The asymmetric unit contains two copies of the β subunit that are related by a non-crystallographic symmetry (NCS) two-fold axis, both copies of which contain proteolytic cleavages after amino acid 100. It is noteworthy that the oligosaccharide moieties covalently attached at asparagine 13 were particularly pronounced in the electron density, allowing seven sugar residues to be defined. The α subunit of LH, which is common to all glycosylated gonadotropin hormones, was placed by superposition of hCG on the LH beta subunits, thereby yielding a model for the intact hormone.
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Affiliation(s)
- Steven B. Larson
- Dept. Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, USA
| | - Alexander McPherson
- Dept. Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, USA
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2
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Jiang X, Dias JA, He X. Structural biology of glycoprotein hormones and their receptors: insights to signaling. Mol Cell Endocrinol 2014; 382:424-451. [PMID: 24001578 DOI: 10.1016/j.mce.2013.08.021] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 08/20/2013] [Accepted: 08/24/2013] [Indexed: 01/18/2023]
Abstract
This article reviews the progress made in the field of glycoprotein hormones (GPH) and their receptors (GPHR) by several groups of structural biologists including ourselves aiming to gain insight into GPH signaling mechanisms. The GPH family consists of four members, with follicle-stimulating hormone (FSH) being the prototypic member. GPH members belong to the cystine-knot growth factor superfamily, and their receptors (GPHR), possessing unusually large N-terminal ectodomains, belong to the G-protein coupled receptor Family A. GPHR ectodomains can be divided into two subdomains: a high-affinity hormone binding subdomain primarily centered on the N-terminus, and a second subdomain that is located on the C-terminal region of the ectodomain that is involved in signal specificity. The two subdomains unexpectedly form an integral structure comprised of leucine-rich repeats (LRRs). Following the structure determination of hCG in 1994, the field of FSH structural biology has progressively advanced. Initially, the FSH structure was determined in partially glycosylated free form in 2001, followed by a structure of FSH bound to a truncated FSHR ectodomain in 2005, and the structure of FSH bound to the entire ectodomain in 2012. Comparisons of the structures in three forms led a proposal of a two-step monomeric receptor activation mechanism. First, binding of FSH to the FSHR high-affinity hormone-binding subdomain induces a conformational change in the hormone to form a binding pocket that is specific for a sulfated-tyrosine found as sTyr 335 in FSHR. Subsequently, the sTyr is drawn into the newly formed binding pocket, producing a lever effect on a helical pivot whereby the docking sTyr provides as the 'pull & lift' force. The pivot helix is flanked by rigid LRRs and locked by two disulfide bonds on both sides: the hormone-binding subdomain on one side and the last short loop before the first transmembrane helix on the other side. The lift of the sTyr loop frees the tethered extracellular loops of the 7TM domain, thereby releasing a putative inhibitory influence of the ectodomain, ultimately leading to the activating conformation of the 7TM domain. Moreover, the data lead us to propose that FSHR exists as a trimer and to present an FSHR activation mechanism consistent with the observed trimeric crystal form. A trimeric receptor provides resolution of the enigmatic, but important, biological roles played by GPH residues that are removed from the primary FSH-binding site, as well as several important GPCR phenomena, including negative cooperativity and asymmetric activation. Further reflection pursuant to this review process revealed additional novel structural characteristics such as the identification of a 'seat' sequence in GPH. Together with the 'seatbelt', the 'seat' enables a common heteodimeric mode of association of the common α subunit non-covalently and non-specifically with each of the three different β subunits. Moreover, it was possible to establish a dimensional order that can be used to estimate LRR curvatures. A potential binding pocket for small molecular allosteric modulators in the FSHR 7TM domain has also been identified.
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Affiliation(s)
- Xuliang Jiang
- EMD Serono Research & Development Institute, Billerica, MA 01821, United States.
| | - James A Dias
- Department of Biomedical Sciences, School of Public Health, University at Albany-SUNY, Albany, NY 12222, United States
| | - Xiaolin He
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, United States
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3
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Perera-Marín G, Murcia C, González-Padilla E. Luteinizing hormone (LH) isoforms in ruminants: Characterization and physiological relevance. Anim Reprod Sci 2007; 101:187-207. [DOI: 10.1016/j.anireprosci.2007.03.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Accepted: 03/09/2007] [Indexed: 11/16/2022]
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4
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Borrelli L, De Stasio R, Bovenzi V, Parisi E, Filosa S. Responsiveness of adenylate cyclase to pituitary gonadotropins and evidence of a hormone-induced desensitization in the lizard ovary. Gen Comp Endocrinol 1997; 107:23-31. [PMID: 9208303 DOI: 10.1006/gcen.1997.6893] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Gonadotropins (FSH and LH) affect several mammalian gonadal functions. In particular, FSH stimulates oogonial proliferation and oocyte growth, while LH regulates ovulation and progesterone secretion. In lacertilian reptiles, gonadal function is also regulated by pituitary gonadotropins, but which hormone controls ovarian activities and the mechanisms of action are unknown. The present study aimed to clarify mechanisms of action of pituitary gonadotropins on the ovary of Podarcis sicula (Lacertilia). The data demonstrate that mammalian gonadotropins FSH and LH produce a threefold stimulation of adenylate cyclase activity in follicular membranes, while hCG and TSH are less effective, causing a twofold increase in adenylate cyclase activity. Neurotransmitters such as dopamine, serotonin, and catecholamines have no effect on enzyme activity. The action of mammalian FSH and LH on the ovary mimics the effect of homologous hormones: in lizard ovaries incubated in vitro in the presence of isolated homologous pituitary glands, the intracellular cAMP level increased by 50% with respect to control ovaries. Mammalian gonadotropins appear homologous to lizard gonadotropin(s): Southern blot analyses show that the lizard genome contains nucleotide sequences homologous to those encoding for mammalian beta FSH and beta LH. Both homologous and heterologous desensitization of adenylate cyclase activity occurs in the lizard ovary. In fact, responsiveness of adenylate cyclase to gonadotropin stimulation is abolished in animals 2 hr after in vivo treatment with FSH. Sensitivity to gonadotropin stimulation is restored 2 weeks after the beginning of the in vivo treatment. Desensitization was also observed in ovaries incubated in vitro with mammalian FSH or with isolated pituitary glands.
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Affiliation(s)
- L Borrelli
- CNR Institute of Protein Biochemistry and Enzymology, Naples, Italy
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5
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Kottler ML, Counis R, Degrelle H. Sex steroid-binding protein: identification and comparison of the primary product following cell-free translation of human and monkey (Macaca fascicularis) liver RNA. JOURNAL OF STEROID BIOCHEMISTRY 1989; 33:201-7. [PMID: 2475674 DOI: 10.1016/0022-4731(89)90295-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A very close similarity in molecular, steroid-binding and immunological properties have been demonstrated for the sex steroid-binding proteins of plasma from human (hSBP) and monkey (mSBP): both are glycoproteins composed of two similar subunits able to bind one steroid molecule and to cross-react with the same antibodies. After translation of human and monkey (Macaca fascicularis) liver mRNAs by a wheat-germ embryo extract, in the presence of labelled amino-acids, we have characterized in both cases a single radioactive polypeptide immunologically related to SBP, migrating in SDS-PAGE as a single band and having a molecular weight of about 42,000. This protein could be displaced from the antibody by pure unlabelled SBP in excess. The difference in molecular weight between the in vitro translation product and the native SBP sub-unit is probably due to the absence of glycosylation in the neo-synthesized protein. The radioactivity incorporated into mSBP was 4 times higher than the radioactivity incorporated into hSBP, suggesting that the amount of mRNA for SBP is higher in monkey than in human liver. Our results show that the two sub-units of hSBP and mSBP derive from a common precursor, representing respectively 0.0050% and 0.0013% of the total neosynthesized proteins in monkey and in human liver.
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Affiliation(s)
- M L Kottler
- Laboratoire de Biochimie Endocrinienne, Paris, France
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Kottler ML, Ribot G, Tardivel-Lacombe J, Counis R, Degrelle H. Identification of the primary translation product of the sex steroid-binding protein from monkey liver mRNA in a cell-free system. Biochimie 1988; 70:1423-27. [PMID: 3148331 DOI: 10.1016/0300-9084(88)90015-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The synthesis of monkey (Macaca fascicularis) Sex steroid-Binding Protein (mSBP) in a wheat germ cell-free system in response to liver RNA was demonstrated by use of a specific antiserum raised against purified native human SBP. Antibodies precipitate a single translation product behaving as a 42 kDa protein in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Western blots of monkey sera subjected to SDS-PAGE and immunorevelation show that the native mSBP migrates as 2 molecular species (50 and 53 kDa) present in the approximate ratio of 1:10, respectively. The difference in apparent molecular weights of the primary translation product and the reduced mature mSBP may represent glycosylation that occurs post translationally. We describe for the first time the biosynthesis of mSBP at the molecular level and suggest that both components of mSBP derive from a common differentially processed precursor. Its mRNA is poorly represented, since the neosynthesized mSBP represents about 0.005% of the total proteins encoded by liver mRNA.
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Affiliation(s)
- M L Kottler
- Laboratoire de Biochimie Endocrinienne, Paris, France
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Starzec A, Jutisz M, Counis R. Detection of a lag phase in gonadotropin-releasing hormone stimulated synthesis of lutropin peptide chains in cultured rat anterior pituitary cells. Biochem Biophys Res Commun 1988; 153:664-70. [PMID: 3289536 DOI: 10.1016/s0006-291x(88)81146-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We have studied the time course (0-5h) of the stimulatory effect of the hypothalamic gonadotropin-releasing hormone (GnRH) on the biosynthesis of lutropin (LH) polypeptide chains, as measured by the incorporation of [35S] methionine into proteins synthesized in cultured rat anterior pituitary cells in the absence or presence of 10nM GnRH. Labeled polypeptides, immunologically related to LH subunits alpha and beta, were isolated by specific immunoprecipitation, analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, then revealed by fluorography and quantified by counting the excised bands. This methodology allowed us to detect the radioactivity incorporated into LH subunits after less than 15 min of incubation. During first 1h of the time-course the quantity of [35S]Met incorporated into both alpha and LH beta subunits was not increased by the presence of GnRH in the incubation medium. A significant increase in the incorporation of radioactivity into LH subunits was observed after 2h of GnRH treatment. However, the increase in LH release into the medium in response to GnRH, as measured by RIA, was immediate. These data demonstrate that GnRH-stimulated synthesis of LH polypeptide chains occurs after a lag of approximately 1h and involves mechanisms different from those governing the stimulation of LH release.
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Affiliation(s)
- A Starzec
- Laboratoire des Hormones Polypeptidiques, Centre National de la Recherche Scientifique, Gif sur Yvette, France
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Starzec A, Counis R, Jutisz M. Several intermediate forms in the processing of rat lutropin subunits as shown by sodium dodecyl sulphate polyacrylamide gel electrophoresis. J Chromatogr A 1988; 440:352-60. [PMID: 3403667 DOI: 10.1016/s0021-9673(00)94538-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
To study the biosynthesis in situ of lutropin (LH) subunits, anterior pituitary cells in culture were employed. The cells were incubated in the presence of [35S]methionine. Labelled polypeptides, immunologically related to alpha and LH beta subunits, were isolated by specific immunoprecipitation, then analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and revealed by fluorography. Electrophoretic analysis of immunoprecipitates is a crucial step in this methodology. It permits simultaneous purification, characterization and accurate quantitation of the radioactivity specifically incorporated into LH subunits. Also, using SDS-PAGE, it is possible to isolate and identify the different processed forms of LH subunits.
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Affiliation(s)
- A Starzec
- Laboratoire des Hormones Polypeptidiques, CNRS, Gif-sur-Yvette, France
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9
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Lerrant Y, Corbani M, Counis R, Jutisz M. Rat placental mRNA directs the synthesis of a polypeptide immunologically related to alpha-subunit of glycoprotein hormones. Mol Cell Endocrinol 1987; 54:23-8. [PMID: 2445607 DOI: 10.1016/0303-7207(87)90135-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In order to investigate the existence of a chorionic gonadotropin (CG) in the rat, placental mRNA was prepared from either the foetal disc or the maternal site of implantation in pregnant rats and translated in a wheat-germ cell-free translation system in the presence of 35S-labeled methionine and cysteine. Sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the radioactive material immunoprecipitated using antiserum specific to native rat alpha-subunit allowed us to isolate in translation products from both sources (foetal disc and maternal site of implantation) a single polypeptide of 17 kDa having the electrophoretic properties of the rat pituitary alpha-precursor. This polypeptide was absent in media derived from translation of mRNA extracted from uterine horn of non-pregnant female rats, and was approximately 10 times more abundant when RNA was derived from the maternal part (about 0.25% of cpm in total proteins) rather than the foetal part (0.026%) of the placenta. Immunoprecipitation was prevented in the presence of an excess of rat (but not ovine) alpha-subunit. Antisera directed against denatured bovine alpha-subunit, which cross-react with the rat pituitary alpha-precursor, did not bind the placental peptide. These results suggest that this rat placental polypeptide and the rat alpha-subunit of pituitary glycoprotein hormones have important differences in their primary structure, but share discrete structurally and/or conformationally related regions in their polypeptide chains. The possibility that these partial homologies account for gonadotropin-like activity of a presumed rat CG remains to be ascertained.
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Affiliation(s)
- Y Lerrant
- Laboratoire des Hormones Polypeptidiques, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
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10
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Bidart JM, Troalen F, Salesse R, Bousfield GR, Bohuon CJ, Bellet DH. Topographic antigenic determinants recognized by monoclonal antibodies on human choriogonadotropin beta-subunit. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47449-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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11
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Abstract
There is evidence that the porcine TSH receptor contains essential disulphide bridge(s) which can be disrupted by dithiothreitol (DTT). The aim of the present study was to determine whether exposure of intact thyroid cells to DTT leads to altered thyroid stimulation. TSH-stimulated iodine organification in cultured porcine thyroid cells was studied following short-term DTT exposure; a dose-dependent inhibition was observed with DTT but not oxidized DTT. Cell viability, follicle formation, and total protein synthesis were preserved. A minimum of 30 min incubation with DTT was required for inhibition. However, under identical conditions, DTT had no effect on TSH or forskolin-stimulated cyclic AMP (cAMP) production. These results suggest that DTT inhibition of organification is mediated by post-receptor mechanisms likely involving thyroid peroxidase. The effects of DTT on thyroid stimulation in vitro does not appear to involve disruption of the disulphide bridge(s) in the TSH receptor.
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Affiliation(s)
- J Ginsberg
- Department of Medicine, University of Alberta, Edmonton, Canada
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12
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13
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Parsons TF, Pierce JG. Studies of the histidine residues of human and bovine glycoprotein hormones by nuclear magnetic resonance. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1983; 21:522-35. [PMID: 6411645 DOI: 10.1111/j.1399-3011.1983.tb02679.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Titration curves of the histidine residues in lutropin, thyrotropin, follitropin and chorionic gonadotropin have been assigned using imidazole C-2 proton nuclear magnetic resonance spectra and their estimated pK values determined. Spectra of reassociated hormone preparations, in which one or the other of their two subunits (alpha or beta) have had their accessible histidines exchanged with deuterium, permitted assignment of C-2 resonance to specific residues. Similar titration curves were found for residues which are conserved from one hormone to another. However, these conserved histidines do not have identical pK values, indicating that differences in the conformation or microenvironment around these residues occur in these hormones. Changes in some pK values also occur as a function of subunit association. The most dramatic change seen in all cases is the exposure to solvent of histidine alpha-83; in isolated alpha subunits this residue is unavailable for titration over a wide pH range. This change appears to be a general consequence of the association of the two subunits in any of these hormones. The data show that all histidines in the intact hormones are accessible to the environment, including those proposed to be in domains involved in subunit-subunit interaction.
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Rathnam P, Tolvo A, Saxena BB. Elucidation of the disulfide bond positions of the beta-subunit of human follicle-stimulating hormone. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 708:160-6. [PMID: 6816284 DOI: 10.1016/0167-4838(82)90216-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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15
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Counis R, Corbani M, Poissonnier M, Jutisz M. Characterization of the precursors of alpha and beta subunits of follitropin following cell-free translation of rat and ovine pituitary mRNAs. Biochem Biophys Res Commun 1982; 107:998-1005. [PMID: 6814434 DOI: 10.1016/0006-291x(82)90621-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Ginsberg J, Smith BR, Hall R. Evidence that the porcine thyrotropin (TSH) receptor contains an essential disulphide bridge. Mol Cell Endocrinol 1982; 26:95-102. [PMID: 6282674 DOI: 10.1016/0303-7207(82)90008-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The effects of reducing agents on membrane bound and detergent solubilised porcine TSH receptors have been investigated. Both 2-mercaptoethanol and dithiothreitol appeared to inhibit the TSH-binding activity by a direct effect on the TSH receptor itself and Scatchard analysis suggested that this was primarily due to an alteration in TSH-binding capacity. In addition, some binding activity could be recovered by reoxidation of reduced receptor preparations. These results suggest therefore that the porcine TSH receptor contains an essential disulphide bridge.
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Reeve JR, Pierce JG. Disulfide bonds of glycoprotein hormones. Their selective reduction in the beta subunits of bovine lutropin and thyrotropin. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1981; 18:79-87. [PMID: 7309370 DOI: 10.1111/j.1399-3011.1981.tb02042.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Fujiki Y, Rathnam P, Saxena BB. Studies on the disulfide bonds in human pituitary follicle-stimulating hormone. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 624:428-35. [PMID: 6774759 DOI: 10.1016/0005-2795(80)90084-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Human follicle-stimulating hormone (FSH) was digested with subtilisin, thermolysin, cyanogen gromide, pronase and trypsin to isolate the cystine-containing peptides. These peptides were purified by gel filtration through Sephadex G-50 column and by high-voltage paper electrophoresis at pH 6, 3.5 and/or 2. The location of the cystine-containing peptides in human FSH alpha- and beta-subunits was established by amino acid composition, end-group analysis and determination of the amino acid sequence by Edman degradation. The results indicate that the disulfide bonds are present between half-cystine residues located between positions 7 and 10, 28 and 87 and 82 and 84 in the alpha-subunit, and between positions 3 and 28, 17 and 51 and 32 and 104 in the beta-subunit of human FSH.
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Weare JA, Reichert LE. Studies with carbodiimide-cross-linked derivatives of bovine lutropin. II. Location of the cross-link and implication for interaction with the receptors in testes. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(18)50270-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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20
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Proton nuclear magnetic resonance studies on bovine lutropin, its subunits, and on the alpha subunit of pregnant mare serum gonadotropin. Assignment of histidine resonances in the alpha subunit. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)30010-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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21
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Giudice L, Pierce J. Studies on the disulfide bonds of glycoprotein hormones. Formation and properties of 11,35-bis(S-alkyl) derivatives of the alpha subunit. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(17)34183-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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22
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Pierce JG, Bloomfield GA, Parsons TF. Purification and receptor binding properties of complexes between lutropin and monovalent antibodies against its alpha subunit. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1979; 13:54-61. [PMID: 217847 DOI: 10.1111/j.1399-3011.1979.tb01849.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A complex between bovine lutropin (LH) and monovalent antibodies (Fab fragments) directed against its alpha subunit, which is common to the glycoprotein hormones, has been purified by gel filtration and chromatography on concanavalin A-Sepharose. The complex is heterogenous with respect to molecular size; 70--80% of the hormone is complexed with either two or three Fab fragments. The LH-Fab alpha complexes retain only about 13% receptor binding activity as compared to LH when measured in a radioligand receptor assay in which the radiolabeled ligand is human choriogonadotropin. (Use of the human hormone as labeled ligand permits direct measurement of competition between receptor and the bovine complex because the alpha portion of the human hormone does not cross react significantly with antibodies directed against bovine alpha subunits.) Complex formation does not lead to dissociation of the lutropin into its subunits, as shown with a homologous LH-beta immunoassay which distinguishes free beta subunit from intact LH. Complexing of LH with Fab-alpha fragments also causes little or no change in the affinity of the hormone's beta subunit for anti-LH-beta antibodies indicating that significant changes in beta subunit conformation did not occur. The data show that at least two well-separated antigenic regions on the alpha subunit are exposed to the surface in the intact hormone. They are also in agreement with the proposal that the loss of binding activity to receptor is due to steric effects rather than to changes in conformation or dissociation, and that there may be sites on the alpha subunit which interact directly with the receptor.
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23
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Ingham KC, Bolotin C. Intrinsic and extrinsic fluorescence probes of subunit interactions in ovine lutropin. Arch Biochem Biophys 1978; 191:134-45. [PMID: 32841 DOI: 10.1016/0003-9861(78)90075-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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24
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Combarnous Y, Nabedryk-Viala E. Porcine lutropin: a study of the association of its subunits by hydrogen-deuterium exchange. Biochem Biophys Res Commun 1978; 84:1119-24. [PMID: 569479 DOI: 10.1016/0006-291x(78)91699-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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25
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Abstract
Incubation of ribonuclease with 0.1M mercaptoethanol at pH 8.5 can increase the enzyme's hydrolytic activity toward cytidine 2',3'-monophosphate (cyclic CMP) under standard assay conditions. Cation-exchange chromatography of the ribonuclease-thiol reaction mixture revealed seven fractions. The fraction with the highest activity had an approximate tenfold decrease in the apparent Michaelis constant for cyclic CMP with respect to native ribonuclease. The enhanced activity is a metastable property since this fraction reverts back to the control activity and chromatographic behavior of native ribonuclease on standing in solution at room temperature.
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26
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Giudice LC, Pierce JG. Studies on the disulfide bonds of glycoprotein hormones. Complete reduction and reoxidation of the disulfide bonds of the alpha subunit of bovine luteinizing hormone. J Biol Chem 1976. [DOI: 10.1016/s0021-9258(20)81874-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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