Study of the superconductivity of metals condensed at 4/sup 0/K

Roberts, J.A.

doi:10.2172/7348051

Cited by 4 publications

(4 citation statements)

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“…It may be regarded as established that the complex high resolution NMR spectrum of a native protein reflects its secondary and tertiary structure [2]. The spectrum of the unfolded form is much simpler and can be approximated by a sum of the spectra of the constituent amino acids.…”

Section: Resultsmentioning

confidence: 99%

Comparison of protein structures by high resolution solid state and solution NMR

Jardetzky

Wade-Jardetzky

1980

FEBS Letters

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Section: Resultsmentioning

confidence: 99%

Comparison of protein structures by high resolution solid state and solution NMR

Jardetzky

Wade-Jardetzky

1980

FEBS Letters

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“…The signals which stem from the carbohydrate moiety have the same chemical shifts for both glycopeptides. The presence of arginine in GP-I1 gives rise to the corresponding extra signals [22]. Relevant NMR data are summarized in Table 3.…”

Section: Resultsmentioning

confidence: 99%

Investigation by 360-MHz 1H-Nuclear-Magnetic-Resonance Spectroscopy and Methylation Analysis of the Single Glycan Chain of Chicken Ovotransferrin

et al. 1979

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The primary structure of two glycopeptides obtained by pronase digestion of chicken ovotransferrin has been investigated by 360-MHz proton nuclear magnetic resonance (NMR) spectroscopy and methylation analysis. The two glycopeptides differ in amino acid composition but contain the same carbohydrate moiety, viz :Using the NMR data of some reference compounds the chemical shifts of the anomeric protons and mannose H-2 protons could be predicted with an accuracy of 0.01 ppm.Ovotransferrin, serotransferrin and lactotransferrin are iron-binding glycoproteins with similar molecular weight and amino acid compositions [1,2]. The primary structure of the N-terminal sequences of the polypeptide chain of these three transferrins shows a close homology [3] and an internal homology of human lactotransferrin and human serotransferrin has recently been described [4]. However, their carbohydrate moieties differ in molar composition, in number as well as in location on the polypeptide chain [2,5 -81. In order to compare the primary structure of ovotransferrin glycan with those of human serotransferrin and lactotransferrin that we have previously determined [9-121 we have undertaken the determination of the ovotransferrin glycan structure. In a preliminary investigation 1131 it was concluded that two possibilities had to be considered for the carbohydrate structure viz. that given in Fig. 3 and an isomeric structure having GlcNAc-7 attached to Man-4' instead of Man-4. The present paper deals with the determination of the structure by 360-MHz 'H-NMR spectroscopy and methylation analysis. MATERIALS AND METHODSIron-free ovotransferrin (type I) from chicken egg white was obtained from Sigma. It consisted of a major and a minor component as was apparent from disc gel electrophoresis. After exhaustive pronase digestion [14] the glycopeptide fraction was purified by gel filtration through a Biogel P 30 column (100 x 2cm) equilibrated in water and then fractionated by paper electrophoresis in 1 M acetic acid, pH 2.4 at 7 V/cm for 18 h. Qualitative and quantitative carbohydrate analyses of the iron-free ovotransferrin and of the glycopeptides were carried out by colourimetry [15] and by gas-liquid chromatography [16].Permethylation of the glycopeptides was performed according to Hakomori [17] and the partially methylated monosaccharides were identified according to Fournet et al. [18,19].The amino acid composition of hydrolyzed glycopeptides (5.6 M HC1, 24 h, 105°C under vacuum) was determined with a Beckman Multichrom analyser. The Edman degradation was carried out according to Konigsberg and Hill [20] and Light and Greenberg [211.

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“…In particular, the highest-field resonance, presumably arising from tyrosine protons, moves progressively downfield, as does another resonance which appears at 3.2 ppm at pH* 2.0; changes in the resonances of Tyr-92 and Tyr-93 have been noted above. The changes are progressive, rather than being characterised by a transition over a narrow pH range, and while the trend is clearly towards a simplification of the spectrum with decreasing pH, the spectrum at pH* 2.0 is not that of a random coil [18,19]. Other regions of the spectrum also show clear indications of a change in conformation below pH* 5.…”

Section: Effects O F P H On the Conjormation Of The CI Subunitmentioning

confidence: 99%

¹H Nuclear‐Magnetic‐Resonance Studies of Porcine Lutropin and Its α and β Subunits

Maghuin‐Rogister

Degelaen

Roberts

1979

European Journal of Biochemistry

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The titration curves of the histidine residues of porcine lutropin and its isolated a and p subunits have been determined by following the pH-dependence of the imidazole C-2 proton resonances. The isolated ci 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 aminoacid sequence, by means of deuterium and tritium exchange experiments on the a subunit and its des(92-96) derivative. The histidine with a pK of 3.3 is identified as His-a87.The effects of pH on tyrosine and methyl proton resonances show that the titration of His-87 in the isolated ci 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.Lut-ropin, like the other glycoprotein hormones thyrotropin, follitropin, choriogonadotropin and pregnant mare serum gonadotropin, consists of two subunits, a and p, associated by non-covalent bonds.Free subunits are not biologically active. Within the same animal species, the a subunit has the same amino acid sequence in the four hormones lutropin, thyrotropin, follitropin and choriogonadotropin [I, 21. The fl subunit thus determines the hormonal specificity of the cip complex, but the association of a hormonespecific p subunit with the common a subunit is mandatory for the expression of hormonal activity.The molecular sites recognised by the receptors, whose occupancy by the specific hormone triggers the biological response of the target cell, are therefore a unique property of the complex of the ci and p subunits. It is thus important to try to characterise in molecular detail the conformational consequences of the subunit association. In a preliminary report [3], we described the presence in the isolated a subunit, but not in the native porcine lutropin, of a histidyl residue Ahhreviuiions. NMR, nuclear magnetic resonance; des(92 -96)-r-subunit, the ct subunit of lutropin with residues 92-96 removed; pH*, pH meter reading uncorrected for the deuterium effect on the glass electrode.Enzymes. CarboxypeptidaseA (EC 3.4.12.2); Carboxypeptidase B (EC 3.4.12.3); Trypsin (EC 3.4.21.4).with an abnormally low pK. We now describe the complete study of the histidyl residues of lutropin, in the isolated a and 0 subunits and in the whole hormone. The assignment of C-2 proton resonances to individual histidines of the lutropin amino-acid sequence has been achieved. The importance of the observed changes on recombination of the subunits for the understanding of the mechanism of action of glycoprotein hormones and the crucial role of the quaternary structure of these hormones in their biological action will be discussed. MATE...

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Study of the superconductivity of metals condensed at 4/sup 0/K

Cited by 4 publications

References 0 publications

Comparison of protein structures by high resolution solid state and solution NMR

Comparison of protein structures by high resolution solid state and solution NMR

Investigation by 360-MHz 1H-Nuclear-Magnetic-Resonance Spectroscopy and Methylation Analysis of the Single Glycan Chain of Chicken Ovotransferrin

¹H Nuclear‐Magnetic‐Resonance Studies of Porcine Lutropin and Its α and β Subunits

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Study of the superconductivity of metals condensed at 4/sup 0/K

Cited by 4 publications

References 0 publications

Comparison of protein structures by high resolution solid state and solution NMR

Comparison of protein structures by high resolution solid state and solution NMR

Investigation by 360-MHz 1H-Nuclear-Magnetic-Resonance Spectroscopy and Methylation Analysis of the Single Glycan Chain of Chicken Ovotransferrin

1H Nuclear‐Magnetic‐Resonance Studies of Porcine Lutropin and Its α and β Subunits

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¹H Nuclear‐Magnetic‐Resonance Studies of Porcine Lutropin and Its α and β Subunits