Le transport de la phénylalanine et de la tyrosine chez Brevibacterium linens : spécificité et incorporation dans les protéines

1984 ◽  
Vol 30 (4) ◽  
pp. 430-438 ◽  
Author(s):  
P. Boyaval ◽  
Evelyne Moreira ◽  
M. J. Desmazeaud
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Cellular Protein ◽  
Cellular Proteins ◽  
Resting Cells ◽  
Brevibacterium Linens ◽  
Competitive Inhibitors ◽  
High Concentrations ◽  
Cellular Protein Synthesis

The specificity of phenylalanine and tyrosine carriers was investigated using actively metabolizing cells of Brevibacterium linens. The cellular protein synthesis of resting cells was very weakly inhibited, even with high concentrations of chloramphenicol or tetracycline. The nonaromatic amino acids were weak inhibitors for these carriers, while fluorinated analogues of phenylalanine and tyrosine were very potent competitive inhibitors. In practice these analogues cannot be used to replace amino acids to evaluate transport without incorporation because they are incorporated in cellular proteins.

The effects of amino acid supply on total and individual cellular protein synthesis in ovine hepatocytes

1999 ◽  
Vol 1999 ◽  
pp. 161-161
Author(s):  
DG Hazlerigg ◽  
N Soultoyiannis ◽  
P Cash ◽  
NM Wheelhouse
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Polyacrylamide Gel Electrophoresis ◽  
Cellular Protein ◽  
Limiting Factor ◽  
Liver Protein ◽  
Animal Products ◽  
Hormonal Signalling ◽  
Cellular Protein Synthesis

Protein nutrition, through altered amino-acid supply, regulates the quality and quantity of animal products, and deficiencies in supply of / response to amino-acids may be a limiting factor in ruminant efficiency. The effects of amino-acid supply may be indirect, via modulation of anabolic hormonal signalling. In particular, amino-acid limitation reduces insulin-like growth factor-1 (IGF-1) - and increases IGF-1 binding protein 1 (IGFBP-1) - production by the liver, and hence modulates the sensitivity of tissues to pituitary GH as an anabolic signal (Gluckman et al, 1987). The mechanisms through which amino-acids exert these selective effects on liver protein production are not understood.The present study sought to determine whether the effects of amino-acids on total cellular protein synthesis are sufficient to account for observed reductions in IGF-1 production in cultured ovine hepatocytes. In addition the use of two dimensional polyacrylamide gel electrophoresis (2D-PAGE) to visualise changes in translation of individual proteins caused by amino-acids in cultured ovine hepatocytes is described.

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.

Effect of adenovirus on metabolism of specific host mRNAs: transport control and specific translational discrimination

1983 ◽  
Vol 3 (7) ◽  
pp. 1212-1221 ◽  
Author(s):  
A Babich ◽  
L T Feldman ◽  
J R Nevins ◽  
J E Darnell ◽  
C Weinberger
Keyword(s):  
Protein Synthesis ◽  
Host Cell ◽  
Cellular Protein ◽  
Host Protein ◽  
Cell Protein ◽  
Viral Mrna ◽  
Initiation Of Translation ◽  
Viral Mutant ◽  
Cellular Mrnas ◽  
Cellular Protein Synthesis

We have studied the adenovirus-induced inhibition of host cell protein synthesis and the effect of infection on the overall metabolism of host cell mRNA during the late phase of adenovirus infection by following the fate of a number of cellular mRNAs complementary to specific cloned DNA segments. At a time in infection when the rate of total cellular protein synthesis is drastically (greater than 90%) reduced, transcription of specific cellular genes is undiminished. However, the transport of newly synthesized cellular mRNA to the cytoplasm is greatly decreased. This decreased appearance of new mRNA in the cytoplasm cannot account for the observed cessation of cell specific protein synthesis, however, since the concentration of several preexisting cellular mRNAs, including the mRNA for actin, remains unchanged throughout the course of infection. The preexisting mRNA is intact, capped, and functional as judged by its ability to direct protein synthesis in vitro in a cap-dependent fashion. The interruption in host translation appears to operate at the level of initiation directly, since we find that fewer ribosomes are associated with a given cellular mRNA after infection than before infection. Furthermore, the in vivo inhibition of cellular protein synthesis does not appear to be the result of competition with viral mRNA, since conditions which prevent the efficient initiation of translation of viral mRNA (infection with a viral mutant) do not result in the recovery of cell translation. Thus, it appears that a late adenovirus gene product directly mediates a shutoff of host protein synthesis.

Normal Cellular Protein Synthesis and Heat Shock

1994 ◽  
pp. 61-76 ◽  
Author(s):  
Mark R. Brodl ◽  
Jacqueline D. Campbell ◽  
Kent K. Grindstaff ◽  
Lora Fielding
Keyword(s):  
Protein Synthesis ◽  
Heat Shock ◽  
Cellular Protein ◽  
Cellular Protein Synthesis

scholarly journals Pinocytosis and intracellular degradation of exogenous protein: modulation by amino acids.

1983 ◽  
Vol 96 (6) ◽  
pp. 1586-1591 ◽  
Author(s):  
J M Besterman ◽  
J A Airhart ◽  
R B Low ◽  
D E Rannels
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Free Amino Acids ◽  
Free Amino ◽  
De Novo ◽  
Serum Proteins ◽  
Fluid Phase ◽  
Cellular Protein ◽  
Intracellular Degradation ◽  
Exogenous Protein

Intracellular degradation of exogenous (serum) proteins provides a source of amino acids for cellular protein synthesis. Pinocytosis serves as the mechanism for delivering exogenous protein to the lysosomes, the major site of intracellular degradation of exogenous protein. To determine whether the availability of extracellular free amino acids altered pinocytic function, we incubated monolayers of pulmonary alveolar macrophages with the fluid-phase marker, [14C]sucrose, and we dissected the pinocytic process by kinetic analysis. Additionally, intracellular degradation of endogenous and exogenous protein was monitored by measuring phenylalanine released from the cell monolayers in the presence of cycloheximide. Results revealed that in response to a subphysiological level of essential amino acids or to amino acid deprivation, (a) the rate of fluid-phase pinocytosis increased in such a manner as to preferentially increase both delivery to and size of an intracellular compartment believed to be the lysosomes, (b) the degradation of exogenously supplied albumin increased, and (c) the fraction of phenylalanine derived from degradation of exogenous albumin and reutilized for de novo protein synthesis increased. Thus, modulation of the pinosome-lysosome pathway may represent a homeostatic mechanism sensitive to the availability of extracellular free amino acids.

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