Synthesis in ribosomes

Linezolid stops protein synthesis in ribosome by inhibiting formation of initiation complex. 

Cocucci, S. and Bagni, N., Polyamine-induced activation of protein synthesis in ribosomal preparation from Helianthus tuberosus tissue, Life Sci., 7, 113-120, 1968. 

Nucleoprotein Nucleic acid RNA-bound protein (protein synthesis in ribosome)... 

Transfer RNA (tRNA) molecules are relatively small RNA molecules that transport amino acids to the site of protein synthesis in ribosomes. 

Ribosomes are ancient ribonucleoprotein complexes that are the sites of protein synthesis in living cells. Their core structures and fundamental functional mechanisms have been conserved throughout the three domains of life bacteria, archaea and eukaryotes. All ribosomes are organized into two subunits that are defined by their apparent sedimentation coefficient, measured in Svedberg units (S). There is a general... 

A ribosome is a cytoplasmic nucleoprotein stmcture that acts as the machinery for the synthesis of proteins from the mRNA templates. On the ribosomes, the mRNA and tRNA molecules interact to translate into a specific protein molecule information transcribed from the gene. In active protein synthesis, many ribosomes are associated with an mRNA molecule in an assembly called the polysome. 

The process of RNA synthesis in bacteria—depicted in Figure 37-3—involves first the binding of the RNA holopolymerase molecule to the template at the promoter site to form a PIC. Binding is followed by a conformational change of the RNAP, and the first nucleotide (almost always a purine) then associates with the initiation site on the 3 subunit of the enzyme. In the presence of the appropriate nucleotide, the RNAP catalyzes the formation of a phosphodiester bond, and the nascent chain is now attached to the polymerization site on the P subunit of RNAP. (The analogy to the A and P sites on the ribosome should be noted see Figure... 

Other antibiotics inhibit protein synthesis on all ribosomes (puromycin) or only on those of eukaryotic cells (cycloheximide). Puromycin (Figure 38—11) is a structural analog of tyrosinyl-tRNA. Puromycin is incorporated via the A site on the ribosome into the carboxyl terminal position of a peptide but causes the premature release of the polypeptide. Puromycin, as a tyrosinyl-tRNA analog, effectively inhibits protein synthesis in both prokaryotes and eukaryotes. Cycloheximide inhibits peptidyltransferase in the 60S ribosomal subunit in eukaryotes, presumably by binding to an rRNA component. 

Of the fonr possible optical isomers of chloramphenicol, only the o-threo form is active. This antibiotic selectively inhibits protein synthesis in bacterial ribosomes by binding to the 50S subunit in the region of the A site involving the 23 S rRNA. The normal binding of the aminoacyl-tRNA in the A site is affected by chloramphenicol in such a... 

A major difference between the classical transmitters and peptides is that the production of a peptide is quite different since the synthesis of a peptide is in the form of a huge precursor of about 300 amino acids which is produced in the nucleus of the cell and then transported to the terminal being processed en route (Fig. 12.1). The prepropeptide is produced by translation in ribosomes and so occurs only in cell bodies or dendrites while the classical transmitters are produced at the terminal via a short series of enzymatic steps from a simple precursor. The study of the production of the propeptides have revealed a series of principles in that ... 

The ribosome is a ribozyme this is how Cech (2000) commented on the report by Nissen et al. (2000) in Science on the successful proof of ribozyme action in the formation of the peptide bond at the ribosome. It has been known for more than 30 years that in the living cell, the peptidyl transferase activity of the ribosome is responsible for the formation of the peptide bond. This process, which takes place at the large ribosome subunit, is the most important reaction of protein biosynthesis. The determination of the molecular mechanism required more than 20 years of intensive work in several research laboratories. The key components in the ribosomes of all life forms on Earth are almost the same. It thus seems justified to assume that protein synthesis in a (still unknown) common ancestor of all living systems was catalysed by a similarly structured unit. For example, in the case of the bacterium E. coli, the two subunits which form the ribosome consist of 3 rRNA strands and 57 polypeptides. Until the beginning of the 1980s it was considered certain that the formation of the peptide bond at the ribozyme could only be carried out by ri-bosomal proteins. However, doubts were expressed soon after the discovery of the ribozymes, and the possibility of the participation of ribozymes in peptide formation was discussed. 

Transcription and protein synthesis in the chloroplast can be inhibited by antibiotics because chloroplast ribosomes are similar in structure to those of bacteria. Chloroplast ribosomes are 70S in size, comprising a large 50S subunit (containing... 

The answer is b. (Hardman, p 1131.) Chloramphenicol inhibits protein synthesis in bacteria and, to a lesser extent, in eukaryotic cells. The drug binds reversibly to the. 505 ribosomal subunit and prevents attachment of aminoacybtransfer RNA (tRNA) to its binding site. The amino acid substrate is unavailable for peptidyl transferase and peptide bond formation. 

Ribosome inactivating cytotoxic protein that irreversibly inhibits protein synthesis in cells, causing cell death. It is a solid obtained from bacteria (Shigella dysenteriae). 

Ribosome activating cytotoxic proteins that irreversibly inhibit protein synthesis in cells, causing cell death. They are obtained from bacteria (Escherichia coli serotype 0157 H7). Verotoxin 1 is almost identical to shiga toxin (C16-A032) and differs only by a single amino acid. Verotoxin 2 has significant differences. 

Finally, this section has focused almost entirely on axonal transport, but dendritic transport also occurs [25]. Since dendrites usually include postsynaptic regions while most axons terminate in presynaptic elements, the dendritic and axonal transport each receive a number of unique proteins. An added level of complexity for intraneuronal transport phenomena is the intriguing observation that mRNA is routed into dendrites where it is implicated in local protein synthesis at postsynaptic sites, but ribosomal components and mRNA are largely excluded from axonal domains [26]. Regulation of protein synthesis in dendritic compartments is an important mechanism is synaptic plasticity [27,28]. The importance of dendritic mRNA transport and local protein synthesis is underscored by the demonstration that the mutation associated with Fragile X syndrome affects a protein important for transport and localization of mRNA in dendrites [27, 29], Similar processes of mRNA transport have been described in glial cells [30]. 

Ehrlich, W., M Mangir, and E.R. Lochmann. 1987. The effect of pentachlorophenol and its metabolite tetrachlorohydroquinone on RNA, protein, and ribosome synthesis in Saccharomyces cells. Ecotoxicol. Environ. Safety 13 7-12. 

Microscopic examination of the mature neutrophils reveals two striking features a single multilobed nucleus and a dense, granular appearance of the cytoplasm (see Fig. 1.1a). The nucleus typically comprises two to four segments, and within this organelle the chromatin is coarsely clumped. Until recently, this abnormal chromatin structure was taken as evidence that the nucleus was transcriptionally inactive however, it is now appreciated that the mature neutrophil does perform active transcription ( 7.3), although rates of biosynthesis are somewhat lower than those observed in cells such as monocytes. There is no detectable nucleolus, so there can be only limited synthesis of ribosomal RNA in these cells. 

A strong link between the phosphorylation of nucleolin, its proteolysis and the production of ribosomal RNA has been observed (Bouche et al, 1984 Bourbon et al, 1983 Warrener and Petryshyn, 1991). The inhibition of proteolysis using leupeptin leads to a lower rRNA transcription in an in vitro transcription system (Bouche et al, 1984). In another series of experiments, the injection of nucleolin antiserum leads to 2-3.5 fold stimulation of pre-rRNA synthesis in Chironomus tentans salivary glands (Egyhazi et al, 1988), although it was not clearly demonstrated that these antibodies blocked specifically the homolog of nucleolin in this species. A model was proposed based on these observations where nucleolin was... 

Bose S, Basu M, Banerjee AK (2004) Role of nucleolin in human parainfluenza virus type 3 infection of human lung epithelial cells. J Virol 78 8146-8158 Bouche G, Caizergues-Ferrer M, Bugler B, Amalric F (1984) Interrelations between the maturation of a 100 kDa nucleolar protein and pre rRNA synthesis in CHO cells. Nucleic Acids Res 12 3025-3035 Bouche G, Gas N, Prats H, Baldin V, Tauber JP, Teissie J, Amalric F (1987) Basic fibroblast growth factor enters the nucleolus and stimulates the transcription of ribosomal genes in ABAE cells undergoing GO-Gl transition. Proc Natl Acad Sci U S A 84(19) 6770-6774. 

Suzuki N, Kobayashi M, Sahara K, Suzuki T, Hosoya T (1991) Synergistic stimulatory effect of glucocorticoid, EGF and insulin on the synthesis of ribosomal RNA and phosphorylation of nucleolin in primary cultured rat hepatocytes. Biochim Biophys Acta 1092 367-375 Suzuki N, Matsui H, Hosoya T (1985) Effects of androgen and polyanrines on the phosphorylation of nucleolar proteins from rat ventral prostates with particular reference to 110-kDa phosphoprotein. J Biol Chem 260 8050-8055... 

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