Inhibition of rat liver aminoacyl-tRNA synthetases in vitro after acute and chronic aflatoxin B1 administration in vivo

1981 ◽  
Vol 37 (1-2) ◽  
pp. 233-244 ◽  
Author(s):  
Gunter Wagner ◽  
Anna Maria Unterreiner
Keyword(s):  
Rat Liver ◽  
Aflatoxin B1 ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases

scholarly journals Lysyl-tRNA synthetase from Escherichia coli K12. Chromatographic heterogeneity and the lysU-gene product

1987 ◽  
Vol 248 (1) ◽  
pp. 43-51 ◽  
Author(s):  
J Charlier ◽  
R Sanchez
Keyword(s):  
Escherichia Coli ◽  
Gene Product ◽  
Activity Ratio ◽  
Deae Cellulose ◽  
Trna Synthetase ◽  
Trna Synthetases ◽  
E Coli ◽  
Aminoacyl Trna Synthetases

In contrast with most aminoacyl-tRNA synthetases, the lysyl-tRNA synthetase of Escherichia coli is coded for by two genes, the normal lysS gene and the inducible lysU gene. During its purification from E. coli K12, lysyl-tRNA synthetase was monitored by its aminoacylation and adenosine(5′)tetraphospho(5′)adenosine (Ap4A) synthesis activities. Ap4A synthesis was measured by a new assay using DEAE-cellulose filters. The heterogeneity of lysyl-tRNA synthetase (LysRS) was revealed on hydroxyapatite; we focused on the first peak, LysRS1, because of its higher Ap4A/lysyl-tRNA activity ratio at that stage. Additional differences between LysRS1 and LysRS2 (major peak on hydroxyapatite) were collected. LysRS1 was eluted from phosphocellulose in the presence of the substrates, whereas LysRS2 was not. Phosphocellulose chromatography was used to show the increase of LysRS1 in cells submitted to heat shock. Also, the Mg2+ optimum in the Ap4A-synthesis reaction is much higher for LysRS1. LysRS1 showed a higher thermostability, which was specifically enhanced by Zn2+. These results in vivo and in vitro strongly suggest that LysRS1 is the heat-inducible lysU-gene product.

Inhibition of Aminoacyl-tRNA Synthetases From Rat Liver by Reducing Agents

1973 ◽  
Vol 51 (11) ◽  
pp. 1537-1541 ◽  
Author(s):  
Rocío Vargas ◽  
Mario Castaneda
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Enzyme Preparation ◽  
Reducing Agents ◽  
Trna Synthetases ◽  
Ph Values ◽  
Aminoacyl Trna Synthetases ◽  
Ethanesulfonic Acid ◽  
Hydroxyethyl Piperazine

Commonly used reducing agents 2-mercaptoethanol and dithiothreitol inhibit in vitro homologous aminoacylation of rat liver systems. The extent of inhibition depends on the buffer and is greater in Tris than in N-2-hydroxyethyl piperazine-N′-2-ethanesulfonic acid (HEPES). Variations in the values of pH and the concentrations of Mg2+, ATP, tRNA, enzyme preparation, and buffers were ineffective to reverse the inhibition produced by these reducing agents. Enzyme activity with no reducing agent is, in general, the same or higher in Tris than in HEPES, although it depends on the pH values and the concentrations of buffer and Mg2+ in the reaction mixture.

scholarly journals The effect of aflatoxin B1 on normal and cortisol-stimulated rat liver ribonucleic acid synthesis

1972 ◽  
Vol 130 (2) ◽  
pp. 619-629 ◽  
Author(s):  
G. E. Neal
Keyword(s):  
Rna Polymerase ◽  
Rat Liver ◽  
Aflatoxin B1 ◽  
Polymerase Activity ◽  
Enzymic Activity ◽  
Target Area ◽  
Receptor Sites ◽  
Rna Polymerase Activity

1. Aflatoxin B1, administered in vivo, inhibits the incorporation of [14C]orotic acid in vivo into rat liver nuclei, and also inhibits both Mg2+- and Mn2+-dependent RNA polymerase activities in nuclei assayed in vitro. 2. Aflatoxin B1 inhibits the cortisol-induced increase in incorporation of [14C]leucine in vivo, but does not affect the control value of this activity. 3. Aflatoxin B1 administered in vivo inhibits the increase in nuclear Mg2+-dependent RNA polymerase activity, assayed in vitro, which results from the treatment with cortisol. 4. Adrenalectomy causes a decrease in Mg2+-dependent RNA polymerase activity. The effect on this enzymic activity of adrenalectomy plus treatment with aflatoxin B1 is no greater than that of treatment with aflatoxin B1 alone. 5. These results suggest that the inhibition of cortisol-stimulated biochemical pathways by aflatoxin B1 is due to an inhibition of cortisol-stimulated RNA synthesis. 6. The cytoplasmic action of aflatoxin is thought to be due to a competition for receptor sites on the endoplasmic reticulum between steroid hormones and aflatoxin B1. No evidence was obtained for a similar competition for nuclear receptor sites between [3H]cortisol and aflatoxin B1. 7. No differences were observed between the activities of RNA polymerase preparations solubilized from control or aflatoxin-inhibited nuclei. 8. No differences in ‘melting’ profiles were observed between DNA and chromatin preparations isolated from control nuclei or from aflatoxin-inhibited nuclei. 9. It is suggested that aflatoxin B1 exerts its effect on RNA polymerase by decreasing the template capacity of the chromatin and that the aflatoxin ‘target’ area of the chromatin includes that region which is stimulated by cortisol. This process, however, does not involve inhibiting the movement of cortisol from the outside of the hepatic cell to the nuclear chromatin.

Effect of X-irradiation on gene expression of rat liver chemokines: in vivo and in vitro studies

2008 ◽  
Vol 46 (01) ◽  
Author(s):  
F Moriconi ◽  
H Christiansen ◽  
H Christiansen ◽  
N Sheikh ◽  
J Dudas ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rat Liver ◽  
In Vitro Studies ◽  
X Irradiation
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