Parathyroid hormone (PTH) fragments relax the guinea-pig trachea in vitro
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Abstract:
Synthetic bovine parathyroid hormone fragment containing the N-terminal 1 – 34 amino acids (bPTH-(1 – 34)) relaxed the guinea-pig trachea constricted with histamine in vitro. Peptides with bovine and human sequences purchased from Peninsula Laboratories and Beckman Bioproducts produced similar effects. Substitution of methionine in positions 8 and 18 by norleucine did not affect this property of bPTH-(1 – 34). However, when the methionines were oxidized by treating the peptide with hydrogen peroxide, the peptide could no longer produce relaxation in the trachea. Oxidation of the methionine-replaced analog did not affect the action of the peptide on the trachea. It seems that the methionines per se are not necessary, but once oxidized the conformation of the molecule may be sufficiently altered to affect its ability to relax the trachea. While propranolol can block the relaxing action of isoproterenol, this blocking agent produces no inhibition of the bPTH-(1 – 34) effect. This action of PTH on the trachea may be related to cAMP because isobutyryl-methylxanthine, a phosphodiesterase inhibitor, potentiates and imidazole, a phosphodiesterase stimulator, inhibits the trachea relaxing action of bPTH-(1 – 34).Keywords:
Norleucine
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Norleucine
Parathyroid hormone receptor
Growth-hormone-releasing hormone receptor
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The methionine analog norleucine was produced during the synthesis of bovine somatotropin by Escherichia coli strain W 3 110G containing the recombinant plasmid pBGH1.Norleucine was generated by the leucine biosynthetic pathway from pyruvate or a-ketobutyrate in place of a-ketoisovalerate as the initial substrate.The intracellular level of norleucine was high enough to permit the analog to compete successfully with methionine for incorporation into protein.Two ways were found to prevent either the formation of norleucine or its incorporation into protein.The endogenous synthesis of norleucine was eliminated by deleting the leucine operon.The addition of sufficient methionine or 2-hydroxy-4-methylthiobutanoic acid, a precursor of methionine, to the culture medium prevented any norleucine from being incorporated into protein.
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Norleucine
Ethionine
Methionine sulfoxide
Alanine
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This paper forms part VI in the series of the crystal structures of hydrophobic amino acids. A low-temperature form (120 K) of dl-norleucine (2-aminohexanoic acid, C6H13NO2), has been solved and refined in the space group C2/c. Molecular packing and cell parameters correlate very well with those proposed for the β-form of dl-norleucine as deduced by Mathieson [Acta Cryst. (1953), 6, 399–403]. Estimated standard deviations betweeen heavy atoms are 0.001–0.002 Å.
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The effects of reported methionine analogs on seedling growth of cowpea ( Vigna unguiculata L.) were studied. L‐methionine‐DL‐sulfoximine (MS) was the most toxic, followed in order by ethionine, a‐methyl methionine (MM), and norleucine. Application of methionine protected seedlings from the inhibitory effects of ethionine and MM. Simultaneous addition of lysine and threonine in nutrient solution did not inhibit seedling growth, while methionine at 300 ppm was partially inhibitory. Screening of 33,000 M 2 seedlings from ethylmethane sulfonate‐treated seeds resulted in the recovery of one plant resistant to ethionine and one resistant to MM. The latter was not viable. Seeds produced from plants grown in nutrient solution plus 200 ppm methionine contained approximately 10% more protein, total methionine, and free methionine in comparison to seeds produced in the absence of exogenous methione.
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Norleucine
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Methionine sulfoxide
Ethionine
Methionine synthase
Norleucine
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Abstract We replaced the single N‐terminal methionine in heterologously expressed human Cu/Zn superoxide dismutase with the non‐canonical methionine analogues homopropargylglycine and norleucine in the yeast Saccharomyces cerevisiae . Our non‐canonical amino acid incorporation protocol involves a two‐step procedure. In the first step, the methionine auxotrophic yeast cells are accumulated in synthetic medium containing methionine while the target protein production is shut off. After a short methionine depletion phase, the cells are transferred to inducing medium that contains the methionine analogue instead of methionine and target protein expression is switched on. The initially low level incorporation of ∼12% could be elevated to 40% by increasing the non‐canonical amino acid concentration in the medium by 10‐fold. With this approach we were able to produce up to 5 mg substituted protein per litre of yeast culture. Copyright © 2008 John Wiley & Sons, Ltd.
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Norleucine
Isoleucine
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Control of methionine biosynthesis in Escherichia coli K12 was reinvestigated by using methionine-analogue-resistant mutants. Norleucine (NL) and a-methylmethionine (MM) were found to inhibit methionine biosynthesis directly whereas ethionine (Et) competitively inhibited methionine utilization. Adenosylation of Et to generate S-adenosylethionine (AdoEt) by cell-free enzyme from E. coli K12 was demonstrated. Tolerance of increasing concentrations of NL by E. coli K12 mutants is expressed serially as phenotypes NLR, NLREtR, NLRMMR and finally NLREtRMMR. All spontaneous NLR mutants had a metK mutation, whereas NTG-induced mutants had mutations in both the metK and metJ genes. The kinetics of methionine adenosylation by the E. coli K12 cell-free enzyme were found to be similar to those reported for the yeast enzyme, showing the typical lag phase at low methionine concentration and disappearance of this phase when AdoMet was included in the incubation mixture. NL extended the lag phase, and lowered the rate of subsequent methionine adenosylation, but did not affect the shortening of the lag phase of adenosylation by AdoMet.
Ethionine
Norleucine
Methionine synthase
Methionine Adenosyltransferase
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