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Results for “Protein Biosynthesis”

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At least 19 recordsLinked to original sources
PubMed1999

Structural information for explaining the molecular mechanism of protein biosynthesis.

Protein biosynthesis is controlled by a number of proteins external to the ribosome. Of these, extensive structural investigations have been performed on elongation factor-Tu and elongation factor-G. This now gives a rather complete structural picture of the functional cycle of elongation factor-Tu and especially of the elongation phase of protein biosynthesis. The discovery that three domains of elongation factor-G are structurally mimicking the amino-acylated tRNA in the ternary complex of elongation factor-Tu has been the basis of much discussion of the functional similarities and functional differences of elongation factor-Tu and elongation factor-G in their interactions with the ribosome. Elongation factor-G:GDP is now thought to leave the ribosome in a state ready for checking the codon-anticodon interaction of the aminoacyl-tRNA contained in the ternary complex of elongation factor-Tu. Elongation factor-G does this by mimicking the shape of the ternary complex. Other translation factors such as the initiation factor-2 and the release factor 1 or 2 are also thought to mimic tRNA. These observations raise questions concerning the possible evolution of G-proteins involved in protein biosynthesis.

Bacterial Proteins↗
PubMed1977

On the control of ribosomal protein biosynthesis in Escherichia coli. I. Studies on ribosomal protein biosynthesis in amino acid-starved cells.

The rate of individual ribosomal protein synthesis relative to total protein synthesis has been determined in Escherichia coli rel+ and rel- cells, under valyltRNA deprivation. These strains have a temperature-sensitive valyl-tRNA synthetase. Starvation was obtained following transfer to the cells to non-permissive temperature. Ribosomal proteins were obtained by treatment of either total lysates of freeze-thawed lysozyme spheroplasts or ammonium sulphate precipitate of ribosomes, with acetic acid. Differential labelling of the ribosomal proteins was observed in both strains: proteins from the rel+ strain appear more labelled than those from the rel- strain, the rate of labelling of individual proteins being about the same in both strains. Moreover ribosomal proteins were found as stable during starvation as total protein. It is thus concluded that in starving cells individual ribosomal proteins are not synthesized at equal rates. This indicates that the synthesis of ribosomal proteins is not only under the control of the rel gene.

Amino Acids↗
PubMedDate not supplied

[RNA biosynthesis and regulation of protein biosynthesis in the liver of chicks with experimental coccidiosis].

The aim of this work was to investigate the interrelationship between RNA biosynthesis and that of protein in chick liver during experimental coccidiosis induced by E. tenella. The peculiarity of this model is that in the course of this disease protein synthesis is significantly intensified inspite of the fact that the rate of the biosynthesis is rather high under normal conditions. It has been shown that 4 to 6 days after infection incorporation of labeled amino acids into proteins from chick liver subcellular fractions is greatly increased. The most pronounced changes are in ribosomal and mitochondrial fractions as well as in the postribosomal supernatant. At the same time the specific radioactivity of serum albumin excreted by liver was increased by factor 3. These changes in protein biosynthesis are associated with a significant increase of both the content and intensity of biosynthesis of high molecular weight precursors of rRNA as well as with those of mature 18S rRNA. The amount of 28S rRNA and mRNA per cell is practically without any changes whereas the mRNA turnover is somewhat more extensive. The selective accumulation of 18S rRNA is suggested to be responsible for the intensification of protein biosynthesis.

Animals↗
PubMed1975

Separation of myocardial cytoplasmic acidic inhibitor proteins which inhibit hepatic protein biosynthesis in vitro.

Cytoplasmic inhibitor proteins of rabbit and pig myocardium have been separated and their in-vitro effects on hepatic cell-free protein biosynthesis reported. Three protein peaks could be separated from myocardial cytoplasmic pH 5 fraction by DEAE and CM cellulose column chromatography. There was a difference in the elution pattern of the acidic inhibitor proteins obtained from pig and rabbit myocardium. The myocardial acidic inhibitor proteins inhibited a liver cell-free protein biosynthesizing system, but not a myocardial cell-free system.

Amino Acids↗
PubMed1998

Possible evolution of factors involved in protein biosynthesis.

The elongation factors of protein biosynthesis are well preserved through out evolution. They catalyze the elongation phase of protein biosynthesis, where on the ribosome amino acids are added one at a time to a growing peptide according to the genetic information transcribed into mRNA. Elongation factor Tu (EF-Tu) provides the binding of aminoacylated tRNA to the ribosome and protects the aminoester bond against hydrolysis until a correct match between the codon on mRNA and the anticodon on tRNA can be achieved. Elongation factor G (EF-G) supports the translocation of tRNAs and of mRNA on the ribosome so that a new codon can be exposed for decoding. Both these factors are GTP binding proteins, and as such exist in an active form with GTP and an inactive form with GDP bound to the nucleotide binding domain. Elongation factor Ts (EF-Ts) will catalyze the exchange of nucleotide on EF-Tu. This review describes structural work on EF-Tu performed in our laboratory over the last eight years. The structural results provide a rather complete picture of the major structural forms of EF-Tu, including the so called ternary complex of aa-tRNA:EF-Tu:GTP. The structural comparison of this ternary complex with the structure of EF-G:GDP displays an unexpected macromolecular mimicry, where three domains of EF-G mimick the shape of the tRNA in the ternary complex. This observation has initiated much speculation on the evolution of all factors involved in protein synthesis, as well as on the details of the ribosomal function in one part of elongation.

Amino Acid Sequence↗
PubMedDate not supplied

[Effect of tryptophan excess in a diet on amino acid composition of skin collagen and on an initial stage of protein biosynthesis in rat liver].

Protein deficiency and tryptophane load against its background lead to the acid-soluble collagen synthesis in the rat skin. The amino acid composition of the collagen differs from the norm. This is accompanied by changes in the free amino acid pool of blood serum and liver, under tryptophane load the free amino acids pool of the liver increasing twice as high. At the same time protein deficiency increases and tryptophane load decreases the level of tRNA amino acylation with tryptophane in the animal liver. Thus, protein deficiency and tryptophane load against its background cause deep changes in the protein biosynthesis.

Amino Acids↗
PubMed1990

The influence of the concentrations of elongation factors and tRNAs on the dynamics and accuracy of protein biosynthesis.

Computer simulations of the elongation cycle of bacterial protein biosynthesis demonstrate that the accuracy of protein biosynthesis cannot be explained by a mechanism which involves only an initial selection and a proofreading reaction. It is suggested that only a combination of initial selection, proofreading and a retardation of non-cognate flows at the level of the EF-Tu-catalyzed GTPase reaction and the peptidyl transfer can guarantee sufficient accuracy at reasonable costs. According to this view the ribosome functions as an allosteric enzyme which, in both its affinity and enzymatic activity, responds optimally only to the cognate substrate. Detailed calculations show, furthermore, that increasing the concentration of EF-G and EF-Ts above the level prevailing in vivo only slightly increases the rate of elongation. In contrast, increasing the concentration of EF-Tu over aminoacyl-tRNA (aa-tRNA) leads to a sharp decline in the rate of elongation. While varying the concentration of EF-G has no effect on the accuracy of protein synthesis, excess of EF-Tu over aminoacyl-tRNA leads to a large increase in accuracy. These results suggest a mechanism by which the accuracy of protein biosynthesis is preserved during amino acid starvation.

Computer Simulation↗
PubMedDate not supplied

[The intensity of protein biosynthesis in the periodontium].

Protein biosynthesis intensity in clinically healthy gingival tissues is the highest at the age 20-30 and reduces by 40-50. In generalized periodontitis this parameter glows, particularly so in exacerbations. An exacerbation is characterized by similar rises of protein synthesis activity in various degrees of the disease. In chronic periodontitis biosynthesis intensity is the minimal in slight and maximal in severe generalized periodontitis. Increased content of sulfhydryl groups in the gingiva in generalized periodontitis does not depend on the disease severity in an exacerbation; in a chronic course their level is the maximal in slight and minimal in severe generalized periodontitis.

Adult↗
PubMedDate not supplied

[Study of the ultrastructural and functional expression of the hepatocyte genome under conditions of prolonged depression of protein biosynthesis by cycloheximide. III].

Dynamics of changes in mtRNA synthesis and mitochondria ultrastructure is strictly dependent on the level of inhibition of biosynthesis of cytoplasm proteins and "soluble" proteins of mitochondria by cycloheximide in hepatocytes: 1-6 hrs later a progressive weakening of protein synthesis is accompanied by a drop in mtRNA synthesis and essential destruction of mitochondria; from 12 to 24 hrs a partial restoration of protein biosynthesis induces the processes of the above-mentioned indexes normalization.

Animals↗
PubMedDate not supplied

[Factors participating in regulation of protein biosynthesis].

Studies in the processes of protein biosynthesis regulation revealed a close dependence of the biosynthetic processes (synthesis of many precursors of proteins, nucleic acids, lipids, carbohydrates as well as of tricarboxylic cycle acids) on the processes of carboxylation in the organism. A possibility is shown of the biosynthetic processes stimulation by activating the carboxylation processes. On this bases a highly effective method to increase productivity of farm animals and poultry and that for considerable acceleration of the regeneration processes of the damaged tissues and blood with blood less were developed. It is also established that at extremal states of the organism (long complete fasting, late stages of cancer, thyreoid toxicosis, experimental atherosclerosis, etc.) in tissues there occurs biosynthesis of proteins with differing primary structure, physiochemical properties and enzymatic activity as compared to proteins of the normal animals. The same changes in the primary structure and properties of proteins in the process of their biosynthesis are observed with the surplus feeding the animals on certain amino acids aginst a background of protein free ration. Possible mechanisms of changes in the primary structure of proteins in the process of their biosynthesis at extremal states of the organism are under discussion. In experiments in vitro on the tissue preparations, on the cell-free protein-synthetizing systems as well as in experiments with animals in vivo the presence of synergic and antagonistic interrelation was established between certain amino acids in the process of their utilization for protein biosynthesis. These interrelations are established to take place at the stage of transfer ribonucleic acids aminoacylation. Some details of this phenomenon are found out. Amino acids are shown to play not only a substrate role but also the regulatory one in the process of protein biosynthesis.

Amino Acids↗
PubMed1993

[The hormonal regulation of bile secretion due to the activation of protein biosynthesis in the hepatocytes].

The enhanced bile secretion induced by hydrocortisone coincides in time with activation of the biosynthesis of intracellular and export proteins of the liver. Preliminary inhibition of the protein biosynthesis in the hepatocytes hinders the development of hypercholeretic effects of hydrocortisone or considerably distorts them. The activation of the protein biosynthesis in the liver cells is one of the main molecular mechanisms of choleretic action of glycocorticoids and a number of other hormones.

Animals↗