Inhibition of Protein Synthesis in Chloroplasts from Plant Cells by Virginiamycin

1979 ◽  
Vol 34 (12) ◽  
pp. 1195-1198 ◽  
Author(s):  
C. Cocito ◽  
O. Tiboni ◽  
F. Vanlinden ◽  
O. Ciferri
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Synergistic Effect ◽  
Plant Cells ◽  
Inhibitory Effect ◽  
Spinach Chloroplasts ◽  
Inhibition Of Protein Synthesis ◽  
Isolated Chloroplasts

Abstract The light-driven incorporation of amino acids by isolated spinach chloroplasts is inhibited by the M component (VM) and not by the S component (VS) of virginiamycin. This inhibitory effect is partially reversible. In chloroplast extracts, poly(U)-directed polyphenylalanine formation is strongly inhibited by VM and not by VS. The in vivo synergistic effect of VM and VS observed in bacteria and algae, does not occur in isolated chloroplasts and chloroplast extracts.

scholarly journals Effects of inhibition of protein synthesis by cycloheximide on lipogenesis in mammary gland and liver of lactating rats

1982 ◽  
Vol 204 (2) ◽  
pp. 417-423 ◽  
Author(s):  
A F C Roberts ◽  
J R Viña ◽  
M R Munday ◽  
R Farrell ◽  
D H Williamson
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Liver Glycogen ◽  
Glycolytic Flux ◽  
Hepatic Lipogenesis ◽  
Plasma Insulin Concentration ◽  
Inhibition Of Protein Synthesis ◽  
Inhibitor Of Protein Synthesis

1. Administration of cycloheximide (an inhibitor of protein synthesis) to lactating rats raised the concentrations of amino acids, and in particular, the branched-chain amino acids (valine, leucine and isoleucine) in blood, liver and mammary gland. 2. Inhibition of protein synthesis increased the incorporation in vivo of L-[U-14C]leucine into lipids of mammary gland and liver. 3. Cycloheximide treatment caused no immediate change in the overall rate of lipogenesis in vivo (measured with 3H2O) in mammary gland but increased the rate in liver 3-fold; this latter effect also occurred in livers of virgin rats. 4. The increased rate of hepatic lipogenesis was not accompanied by significant changes in the plasma insulin concentration or the activity of acetyl-CoA carboxylase. 5. Although cycloheximide decreased the entry of total triacylglycerol into the circulation it did not alter the rate of secretion of newly synthesized saponifiable lipid. 6. Cycloheximide slightly stimulated lipogenesis from endogenous substrates in isolated hepatocytes, but this effect was abolished when lactate was the exogenous substrate. 7. Administration of cycloheximide to virgin rats decreased liver glycogen and increased the hepatic content of glucose 6-phosphate, pyruvate and lactate. 8. It is concluded that (a) there is no short-term link between the rate of protein synthesis and lipogenesis in the lactating mammary gland and (b) the increased rate of hepatic lipogenesis in cycloheximide-treated rats is mainly due to stimulation of glycogenolysis, glycolytic flux and consequent increased availability of pyruvate.

ACTION OF THYROTROPHIN (TSH) ON THYROID PROTEIN SYNTHESIS IN VIVO AND IN VITRO

1973 ◽  
Vol 72 (3) ◽  
pp. 453-463 ◽  
Author(s):  
Gustav Wägar ◽  
Ragnar Ekholm ◽  
Ulla Björkman
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Free Amino ◽  
Microsomal Fraction ◽  
Inhibitory Effect ◽  
Leucine Incorporation ◽  
Bovine Thyroid ◽  
Stimulation Of

ABSTRACT The effect of TSH on the incorporation of L-14C-leucine into thyroid proteins was studied in vivo in rats as well as in vitro on bovine thyroid slices and a microsomal subfraction. It was found that TSH reduced the incorporation of radio-leucine into the proteins of slices during the first 2 hours when the concentration of non-labelled leucine in the incubation medium was low. When cold leucine was added to the medium this inhibitory effect was no longer observed. After 6 hours a stimulatory effect on the radio-leucine incorporation by TSH was obvious at both low and high leucine concentrations. The incorporation of 14C-leucine into proteins by the microsomal fraction incubated with a pH 5-fraction was reduced by TSH but this inhibitory effect of TSH disapperaed when post-microsomal supernatant, containing free amino acids, was added to the incubation mixture. It is suggested that the apparent inhibitory effect of TSH on protein synthesis in thyroid slices is due to an altered ratio labelled/non-labelled leucine, caused by stimulation of proteolysis by TSH. This explanation does not seem applicable, however, to the similar apparently inhibitory effect of TSH on protein synthesis observed in the microsomal fraction. In the in vivo experiments a stimulation of the incorporation of labelled leucine could not be observed until 4 hours after the TSH administration. It is suggested that this apparently slow effect of TSH on protein synthesis might be explained either by an indirect effect of TSH on protein synthesis or by a TSH-induced change of the ratio labelled/non-labelled leucine.

scholarly journals BIOSYNTHESIS IN ISOLATED ACETABULARIA CHLOROPLASTS

1972 ◽  
Vol 54 (2) ◽  
pp. 279-294 ◽  
Author(s):  
David C. Shephard ◽  
Wendy B. Levin
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Technical Problems ◽  
Hydrolyzed Protein ◽  
Protein Amino Acids ◽  
Amino Acid Labeling ◽  
Labeling Pattern

The ability of chloroplasts isolated from Acetabulana mediterranea to synthesize the protein amino acids has been investigated. When this chloroplast isolate was presented with 14CO2 for periods of 6–8 hr, tracer was found in essentially all amino acid species of their hydrolyzed protein Phenylalanine labeling was not detected, probably due to technical problems, and hydroxyproline labeling was not tested for The incorporation of 14CO2 into the amino acids is driven by light and, as indicated by the amount of radioactivity lost during ninhydrin decarboxylation on the chromatograms, the amino acids appear to be uniformly labeled. The amino acid labeling pattern of the isolate is similar to that found in plastids labeled with 14CO2 in vivo. The chloroplast isolate did not utilize detectable amounts of externally supplied amino acids in light or, with added adenosine triphosphate (ATP), in darkness. It is concluded that these chloroplasts are a tight cytoplasmic compartment that is independent in supplying the amino acids used for its own protein synthesis. These results are discussed in terms of the role of contaminants in the observed synthesis, the "normalcy" of Acetabularia chloroplasts, the synthetic pathways for amino acids in plastids, and the implications of these observations for cell compartmentation and chloroplast autonomy.

Effect of Cycloheximide on In Vitro and In Vivo Protein Synthesis by Certain Tissues of Rats and Pigeons with Special Reference to Muscle

1973 ◽  
Vol 51 (12) ◽  
pp. 933-941 ◽  
Author(s):  
Njanoor Narayanan ◽  
Jacob Eapen
Keyword(s):  
Amino Acids ◽  
Body Weight ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Incorporation ◽  
Contrast Administration ◽  
Acid Incorporation ◽  
Tissue Homogenates

The effect of cycloheximide in vitro and in vivo on the incorporation of labelled amino acids into protein by muscles, liver, kidneys, and brain of rats and pigeons was studied. In vitro incorporation of amino acids into protein by muscle microsomes, myofibrils, and myofibrillar ribosomes was not affected by cycloheximide. In contrast, administration of the antibiotic into intact animals at a concentration of 1 mg/kg body weight resulted in considerable inhibition of amino acid incorporation into protein by muscles, liver, kidneys, and brain. This inhibition was observed in all the subcellular fractions of these tissues during a period of 10–40 min after the administration of the precursor. Tissue homogenates derived from in vivo cycloheximide-treated animals did not show significant alteration in in vitro amino acid incorporation with the exception of brain, which showed a small but significant enhancement.

scholarly journals The rate-limiting step of protein synthesis in vivo and in vitro and the distribution of growing peptides between the puromycinlabile and puromycin-non-labile sites on polyribosomes

1971 ◽  
Vol 122 (3) ◽  
pp. 267-276 ◽  
Author(s):  
D. C. N. Earl ◽  
Susan T. Hindley
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Donor Site ◽  
Peptide Bond ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Donor And Acceptor ◽  
Rate Limiting

1. At 3 min after an intravenous injection of radioactive amino acids into the rat, the bulk of radioactivity associated with liver polyribosomes can be interpreted as growing peptides. 2. In an attempt to identify the rate-limiting step of protein synthesis in vivo and in vitro, use was made of the action of puromycin at 0°C, in releasing growing peptides only from the donor site, to study the distribution of growing peptides between the donor and acceptor sites. 3. Evidence is presented that all growing peptides in a population of liver polyribosomes labelled in vivo are similarly distributed between the donor and acceptor sites, and that the proportion released by puromycin is not an artifact of methodology. 4. The proportion released by puromycin is about 50% for both liver and muscle polyribosomes labelled in vivo, suggesting that neither the availability nor binding of aminoacyl-tRNA nor peptide bond synthesis nor translocation can limit the rate of protein synthesis in vivo. Attempts to alter this by starvation, hypophysectomy, growth hormone, alloxan, insulin and partial hepatectomy were unsuccessful. 5. Growing peptides on liver polyribosomes labelled in a cell-free system in vitro or by incubating hemidiaphragms in vitro were largely in the donor site, suggesting that either the availability or binding of aminoacyl-tRNA, or peptide bond synthesis, must be rate limiting in vitro and that the rate-limiting step differs from that in vivo. 6. Neither in vivo nor in the hemidiaphragm system in vitro was a correlation found between the proportion of growing peptides in the donor site and changes in the rate of incorporation of radioactivity into protein. This could indicate that the intracellular concentration of amino acids or aminoacyl-tRNA limits the rate of protein synthesis and that the increased incorporation results from a rise to a higher but still suboptimum concentration.

scholarly journals Amino acid regulation of synthesis of ribonucleic acid and protein in the liver of rats

1971 ◽  
Vol 124 (2) ◽  
pp. 385-392 ◽  
Author(s):  
R. W. Wannemacher ◽  
C. F. Wannemacher ◽  
M. B. Yatvin
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Free Amino Acids ◽  
Free Amino ◽  
Cellular Protein ◽  
Deficient Diet ◽  
Cellular Protein Content ◽  
Regulate Protein

Weanling (23-day-old) rats were fed on either a low-protein diet (6% casein) or a diet containing an adequate amount of protein (18% casein) for 28 days. Hepatic cells from animals fed on the deficient diet were characterized by markedly lower concentrations of protein and RNA in all cellular fractions as compared with cells from control rats. The bound rRNA fraction was decreased to the greatest degree, whereas the free ribosomal concentrations were only slightly less than in control animals. A good correlation was observed between the rate of hepatic protein synthesis in vivo and the cellular protein content of the liver. Rates of protein synthesis both in vivo and in vitro were directly correlated with the hepatic concentration of individual free amino acids that are essential for protein synthesis. The decreased protein-synthetic ability of the ribosomes from the liver of protein-deprived rats was related to a decrease in the number of active ribosomes and heavy polyribosomes. The lower ribosomal content of the hepatocytes was correlated with the decreased concentration of essential free amino acids. In the protein-deprived rats, the rate of accumulation of newly synthesized cytoplasmic rRNA was markedly decreased compared with control animals. From these results it was concluded that amino acids regulate protein synthesis (1) by affecting the number of ribosomes that actively synthesize protein and (2) by inhibiting the rate of synthesis of new ribosomes. Both of these processes may involve the synthesis of proteins with a rapid rate of turnover.

O.56 Differential response of oxidation to exogenous availability of amino acids to sustain protein synthesis in vivo

1995 ◽  
Vol 14 ◽  
pp. 20
Author(s):  
R. Barazzoni ◽  
M. Zanetti ◽  
M. Vettore ◽  
S. Normand ◽  
D. Bruttomesso ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Differential Response

INDUCTION OF CYTOCHROME P-448 BY 3-METHYLCHOLANTHRENE IN THE RAT DURING INHIBITION OF PROTEIN SYNTHESIS IN VIVO

1977 ◽  
pp. 551-558 ◽  
Author(s):  
Georg F. Kahl ◽  
Bernd Zimmer ◽  
Teresa Galinsky ◽  
Hans G. Jonen ◽  
Regine Kahl
Keyword(s):  
Protein Synthesis ◽  
Inhibition Of Protein Synthesis
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