scholarly journals The effect of trimethoprim on macromolecular synthesis in Escherichia coli. Ribosome maturation in RCstr and RCrel strains

1973 ◽  
Vol 136 (2) ◽  
pp. 235-247 ◽  
Author(s):  
J. E. M. Midgley ◽  
R. J. Smith
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Ribosomal Proteins ◽  
High Rate ◽  
Chain Elongation ◽  
Chain Initiation ◽  
Rna Accumulation ◽  
Ribosomal Protein Synthesis ◽  
Nucleotide Bases

When Escherichia coli was inhibited with trimethoprim in media supplemented with nucleotide bases, glycine and methionine, both RCstr and RCrel strains continued to accumulate RNA at rates very close to those in growing controls. The effects of trimethoprim on protein synthesis were studied by using as an experimental basis the rate of maturation of ribosomal particles from RNA-rich precursors. 1. In RCstr cultures given nucleotide bases but no amino acids, RNA accumulation was inhibited because of amino acid lack. However, maturation of ribosomes from their precursors was more severely inhibited than was the synthesis of rRNA. The restraints on protein synthesis were more severe at the level of translation than the transcription of operons specific for the formation of ribosomal proteins. The kinetic delay time in the passage of rRNA from RNA-rich intermediates to the final ribosome products was therefore increased some three- to four-fold. 2. In RCrel cultures in the same conditions, trimethoprim inhibition stopped ribosomal particle synthesis, but rRNA-rich precursors accumulated. 3. If glycine+methionine were also added to inhibited RCstr cultures, RNA accumulation resumed at a high rate. However, ribosomal maturation was still considerably disturbed because of a disproportionate response of the cells in the formation of protein and RNA. 4. With RCrel cultures, addition of the amino acids caused a large increase in the rate of ribosome maturation, though the degree of disproportionation between the rates of rRNA and ribosomal protein synthesis was now identical with that found in RCstr strains. 5. When inhibited RCrel cultures were supplemented, there was still a severe inhibition of protein synthesis at the level of chain initiation, but inaccuracies in the process of polypeptide chain elongation were greatly decreased. This suggests that the effects of the RCrel mutation on the fidelity of protein synthesis in bacteria are not directed at the point of chain initiation.

scholarly journals The effect of trimethoprim on macromolecular synthesis in Escherichia coli. General effects on ribonucleic acid and protein synthesis

1973 ◽  
Vol 136 (2) ◽  
pp. 225-234 ◽  
Author(s):  
R. J. Smith ◽  
J. E. M. Midgley
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Rna Synthesis ◽  
Protein Chain ◽  
Macromolecular Synthesis ◽  
Chain Initiation ◽  
Chain Polymerization ◽  
Rna Accumulation ◽  
New Protein ◽  
Endogenous Synthesis

In trimethoprim-inhibited RCstr strains of Escherichia coli, the expression of the RC control of stable RNA synthesis arose primarily from a decrease in the intracellular concentrations of glycine and methionine, and not from inhibition of the initiation of new protein chains. In non-supplemented cultures, experiments with rifampicin showed that the immediate response to the addition of trimethoprim was a rapid decrease in the rate of initiation of RNA chains. This was followed after a few minutes by a sufficiently large fall in the rate of endogenous synthesis of nucleotide bases to cause a decrease in the rate of RNA chain polymerization. Inhibition of RNA chain initiation was thus overridden by an accumulation of DNA-dependent RNA polymerases upon the cistrons. RCrel strains also accumulated polymerases upon the DNA in similar circumstances, but did not suffer the initial effects on chain initiation. If purines were supplied before adding trimethoprim, RCstr strains polymerized RNA chains at normal rates, but initiation rates were permanently decreased. In either situation, an increased% of the RNA formed was mRNA. However, in RCrel strains supplemented with bases, trimethoprim did not affect either the rate of initiation of new chains or their rates of polymerization or the relative rates of synthesis of stable RNA and mRNA. Protein synthesis was also severely inhibited by trimethoprim. Though the addition of glycine and methionine to base-supplemented, trimethoprim-inhibited RCstr strains did not apparently affect the decreased rate of protein synthesis, RNA accumulation resumed at its normal rate. Thus, the inhibition of protein chain initiation had no effect on the rate of RNA accumulation in either RCstr or RCrel bacteria. The RC control does not express itself through inhibitions of protein synthesis at this level.

scholarly journals Precocious germination and its regulation in embryos of triticale caryopses

2014 ◽  
Vol 56 (3) ◽  
pp. 469-483 ◽  
Author(s):  
Stanisław Weidner
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Control Sample ◽  
Precocious Germination ◽  
Mature Embryos ◽  
Triticale Caryopses ◽  
Ribosomal Protein Synthesis ◽  
Stimulation Of

Triticale var. Lasko embryos, isolated from grain gathered at milk ripeness, the beginning of wax ripeness and at full ripeness, were allowed to germinate for 48 h on agar with glucose. The highest incorporation of tritiated adenosine into polyribosomal RNA during germination was found in the ribosome fractions from embryos of grain gathered at full ripeness, lower incorporation was in preparations from embryos of milk ripe grain and the lowest in preparations from embryos of wax ripe grain. Different tendencies were observed in respect to the synthesis of ribosomal proteins. The highest incorporation of <sup>14</sup>C-amino acids into ribosomal proteins was found in preparations of ribosome fractions from embryos of milk ripe grain, lower in preparations of embryos from fully ripe grain, the lowest in preparations of embryos from wax ripe grain. ABA (10<sup>-4</sup> M) completely inhibited the external symptoms of germination of immature embryos, while its inhibition of the synthesis of polyribosomal RNA and ribosomal proteins was greater the more mature the embryos that were germinated. The greatest stimulation of precocious germination by exogenous BA and GA<sub>3</sub> was demonstrated in the least mature embryos isolated from milk ripe grain. Under the influence of both stimulators, an increase of the proportion of polyribosomes in the total ribosome fraction occurred in this sample, as did a rise in the intensity of ribosomal protein synthesis. The incorporation of <sup>3</sup>H-adenosine into polyribosomal RNA, however, was lower than in the control sample. The results obtained suggest that the regulation of precocious germination of triticale embryos by phyto-hormones is not directly related to transcription.

scholarly journals A DEAD-box protein regulates ribosome assembly through control of ribosomal protein synthesis

2019 ◽  
Vol 47 (15) ◽  
pp. 8193-8206 ◽  
Author(s):  
Isabelle Iost ◽  
Chaitanya Jain
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Proteins ◽  
Ribosomal Subunit ◽  
Large Family ◽  
Ribosome Assembly ◽  
Protein Abundance ◽  
Ribosomal Assembly ◽  
Dead Box ◽  
Ribosomal Protein Synthesis ◽  
Intrinsic Transcription Termination

Abstract DEAD-box proteins (DBPs) comprise a large family of proteins that most commonly have been identified as regulators of ribosome assembly. The Escherichia coli DBP, SrmB, represents a model bacterial DBP whose absence impairs formation of the large ribosomal subunit (LSU). To define the basis for SrmB function, suppressors of the ribosomal defect of ΔsrmB strains were isolated. The major class of suppressors was found to map to the 5′ untranslated region (UTR) of the rplM-rpsI operon, which encodes the ribosomal proteins (r-proteins) L13 and S9. An analysis of protein abundance indicated that both r-proteins are under-produced in the ΔsrmB strain, but are increased in these suppressors, implicating r-protein underproduction as the molecular basis for the observed ribosomal defects. Reduced r-protein synthesis was determined to be caused by intrinsic transcription termination within the rplM 5′ UTR that is abrogated by SrmB. These results reveal a specific mechanism for DBP regulation of ribosomal assembly, indirectly mediated through its effects on r-protein expression.

scholarly journals Key role of l-alanine in the control of hepatic protein synthesis

1987 ◽  
Vol 241 (2) ◽  
pp. 491-498 ◽  
Author(s):  
D Pérez-Sala ◽  
R Parrilla ◽  
M S Ayuso
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Physiological Role ◽  
Chain Elongation ◽  
Liver Protein ◽  
Isolated Liver Cells ◽  
Metabolic Transformation ◽  
Hepatic Protein Synthesis

We investigated the effects of administration of single amino acids to starved rats on the regulation of protein synthesis in the liver. Of all the amino acids tested, only alanine, ornithine and proline promoted statistically significant increases in the extent of hepatic polyribosome aggregation. The most effective of these was alanine, whose effect of promoting polyribosomal aggregation was accompanied by a decrease in the polypeptide-chain elongation time. The following observations indicate that alanine plays an important physiological role in the regulation of hepatic protein synthesis. Alanine was the amino acid showing the largest decrease in hepatic content in the transition from high (fed) to low (starved) rates of protein synthesis. The administration of glucose or pyruvate is also effective in increasing liver protein synthesis in starved rats, and their effects were accompanied by an increased hepatic alanine content. An increase in hepatic ornithine content does not lead to an increased protein synthesis, unless it is accompanied by an increase of alanine. The effect of alanine is observed either in vivo, in rats pretreated with cycloserine to prevent its transamination, or in isolated liver cells under conditions in which its metabolic transformation is fully impeded.

Suppression of muscle protein turnover and amino acid degradation by dietary protein deficiency

1992 ◽  
Vol 263 (2) ◽  
pp. E317-E325 ◽  
Author(s):  
N. E. Tawa ◽  
A. L. Goldberg
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Dietary Protein ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Normal Diet ◽  
High Rate ◽  
Acid Uptake ◽  
Rapid Weight Gain

To define the adaptations that conserve amino acids and muscle protein when dietary protein intake is inadequate, rats (60-70 g final wt) were fed a normal or protein-deficient (PD) diet (18 or 1% lactalbumin), and their muscles were studied in vitro. After 7 days on the PD diet, both protein degradation and synthesis fell 30-40% in skeletal muscles and atria. This fall in proteolysis did not result from reduced amino acid supply to the muscle and preceded any clear decrease in plasma amino acids. Oxidation of branched-chain amino acids, glutamine and alanine synthesis, and uptake of alpha-aminoisobutyrate also fell by 30-50% in muscles and adipose tissue of PD rats. After 1 day on the PD diet, muscle protein synthesis and amino acid uptake decreased by 25-40%, and after 3 days proteolysis and leucine oxidation fell 30-45%. Upon refeeding with the normal diet, protein synthesis also rose more rapidly (+30% by 1 day) than proteolysis, which increased significantly after 3 days (+60%). These different time courses suggest distinct endocrine signals for these responses. The high rate of protein synthesis and low rate of proteolysis during the first 3 days of refeeding a normal diet to PD rats contributes to the rapid weight gain ("catch-up growth") of such animals.

The resistance of Escherichia coli to oxytetracycline

1969 ◽  
Vol 15 (9) ◽  
pp. 1077-1083 ◽  
Author(s):  
Jerold A. Last ◽  
Kazuo Izaki ◽  
J. F. Snell
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Irreversible Binding ◽  
Resistant Strains ◽  
Growth Of Bacteria

The effects of oxytetracycline on sensitive and resistant strains of Escherichia coli were studied in relation to: (1) growth of bacteria in shaken cultures, (2) incorporation of amino acids into polypeptides by cell-free extracts, (3) binding of aminoacyl-tRNA to ribosomes. Our results support the hypothesis that resistance to the antibiotic is due to impermeability of bacteria to the drug.Evidence is also presented that there is no irreversible binding of oxytetracycline at ribosomal sites involved in protein synthesis.

scholarly journals Effect of heat shock on ribosome synthesis in Drosophila melanogaster.

1988 ◽  
Vol 8 (1) ◽  
pp. 91-95 ◽  
Author(s):  
J Bell ◽  
L Neilson ◽  
M Pellegrini
Keyword(s):  
Tissue Culture ◽  
Protein Synthesis ◽  
Drosophila Melanogaster ◽  
Heat Shock ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
Ribosomal Protein Synthesis ◽  
Correct Processing

In Drosophila tissue culture cells, the synthesis of ribosomal proteins was inhibited by a 1-h 37 degrees C heat shock. Ribosomal protein synthesis was repressed to a greater extent than that of most other proteins synthesized by these cells at 25 degrees C. After a 1-h heat shock, when the cells were returned to 25 degrees C, the ribosomal proteins were much slower than most other 25 degrees C proteins to return to pre-heat shock levels of synthesis. Relative to one another, all the ribosomal proteins were inhibited and later recovered to normal levels of synthesis at the same rate and to the same extent. Unlike the ribosomal proteins, the precursor to the large rRNAs was continually synthesized during heat shock, although at a slightly reduced level, but was not processed. It was rapidly degraded, with a half-life of approximately 16 min. Pre-heat shock levels of synthesis, stability, and correct processing were restored only when ribosomal protein synthesis returned to at least 50% of that seen in non-heat-shocked cells.

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