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G Maghuin-Rogister

Publications and source records attributed to G Maghuin-Rogister.

9 recordsLinked to original sources
PubMed1979

1H nuclear-magnetic-resonance studies of porcine lutropin and its alpha and beta subunits.

The titration curves of the histidine residues of porcine lutropin and its isolated alpha and beta subunits have been determined by following the pH-dependence of the imidazole C-2 proton resonances. The isolated alpha subunit contains a buried histidine, whose C-2 proton does not exchange with solvent, and which has the unusually low pK of 3.3. In the native hormone all the histidine residues have relatively normal pK values (between 5.7 and 6.2). The four histidine C-2 proton resonances have been assigned to specific residues in the amino-acid sequence, by means of deuterium and tritium exchange experiments on the alpha subunit and its des(92-96) derivative. The histidine with a pK of 3.3 is identified as His-alpha87. The effects of pH on tyrosine and methyl proton resonances show that the titration of His-87 in the isolated alpha subunit is accompanied by a significant conformational change which involves loosening of the protein structure but which is not a normal unfolding transition. The role of conformational changes in the generation of biological activity by subunit association in the glycoprotein hormones is discussed.

Animals↗
PubMed1978

Porcine follitropin. The amino-acid sequence of the beta subunit.

The amino acid sequence of the porcine beta subunit has been established by studies of peptides isolated after tryptic, thermolytic and staphylococcal protease treatments of the reduced and carboxymethylated chain. The primary structure of the amino-terminal region of the molecule has been solved by automatic sequencing of the reduced and tritium-labeled carboxymethylated subunit. The amino acid sequence of porcine follitropin beta subunit differs from that of its human counterpart by several amino acid replacements, deletion or addition of one or several residues. The porcine chain appears shorter at both its amino and carboxy-terminal ends. The chemical evolution of follitropin is briefly considered and compared to these of thyrotropin and lutropin.

Amino Acid Sequence↗
PubMed1978

Study of follitropin receptors in testis using a homologous system. Binding of porcine follitropin to plasma membranes from immature porcine testis and correlation with adenylate cyclase stimulation.

The properties of follitropin receptors in immature porcine testis were determined using highly purified porcine follitropin. 1. The characteristics of follitropin binding to a subcellular fraction rich in plasma membranes were studied using a 125I-labelled follitropin with high specific activity (75-100 Ci/g) and high binding activity. The binding is dependent on time, temperature and pH. It is specific to follitropin as demonstrated by the very low binding activity of the follitropin alpha and beta subunits and of the other glycoprotein hormones. Scatchard analysis of binding data indicated an equilibrium association constant of 2 x 10(10) M-1 and a concentration of high affinity binding sites of 500 fmol/mg membrane proteins. 2. A sensitive radio-ligand receptor assay was developed. Fifty percent inhibition of binding was obtained with as little as 2 ng of porcine follitropin. Ovine and bovine follitropins and pregnant mare serum gonadotropin gave binding inhibition curves parallel to that given by porcine follitropin. With equine and human follitropin, significantly different slopes were recorded. 3. Kinetics of dissociation of labelled follitropin from its testis receptors showed the presence of at least two compartments with fast and slow dissociation rate constants. The ratio between the sizes of the slow and fast compartments appeared dependent upon preincubation time. 4. A temporal correlation was observed between binding of follitropin to testis receptors and activation of membrane bound adenylate cyclase.

Adenylyl Cyclases↗
PubMed1977

Bovine follitropin. Isolation and characterization of the native hormone and its alpha and beta subunits.

1) A reproducible procedure was developed for the purification of bovine follitropin. 2) The method involved ammonium sulfate precipitation, ion exchange and adsorption chromatography, concanacaline-A-Sepharose chromatography and gel filtration. 3) A specific radioligand receptor assay was used to monitor each chromatographical step. 4) The potency of highly purified bovine follitropin as measured by Steelman and Pohley bioassay was 62 times the NIH-FSH-B1 standard preparation. 5) Contaminations of bovine follitropin by other glycoprotein hormones such as thyrotropin and lutropin amounted to 3 and 0.45 per cent by weight respectively as measured by specific radioimmunoassays and radioligand receptor assays. 6) The subunits alpha and beta of bovine follitropin were obtained by incubation in acidic urea, the chains being then separated by anion exchange chromatography. The subunits were subjitted to complete characterization. The amino-terminal residue of the alpha subunit is phenylalanine while a half cystine residue was found at the aminoterminal end of the beta chain. 8) Cross-contamination of the alpha and beta subunit preparations was measured by specific radioimmunoassays and amounted to 0.02 and 0.1 per cent by weight respectively.

Amino Acids↗
PubMed1976

Porcine thyrotropin. The amino-acid sequence of the alpha and beta subunits.

The amino acid sequences of both the alpha and beta subunits of porcine thyrotropin have been studied. Bovine thyrotropin primary structure was taken as a model for ordering the tryptic peptides of porcine thyrotropin. The amino acid sequence of the alpha subunit is identical to that of porcine luteinizing hormone, while oligosaccharide side-chains differ in composition. The primary structure of the beta subunit differs from that of bovine thyrotropin by six amino acid replacements, in positions 22, 24, 26, 36, 62 and 69, and by the absence of a methionyl residue at the carboxy terminus. Chemical evolutions of thyrotropin and luteinizing hormone are compared.

Amino Acid Sequence↗