Proteins synthesis on ribosomes

Transfer or soluble RNAs are specific carrier molecules for amino-acids during protein synthesis on ribosomes with ribosomal RNA as the template. There is at least one t-RNA molecule for each amino-acid. 

Peptide bond synthesis Protein synthesis (on ribosomes) ATP, GTP... 

Macrolides inhibit growth of bacteria by inhibiting protein synthesis on ribosomes. Bacterial resistance to macrolides is often accompanied by cross-resistance to lincosamide and sireptogramin B antibiotics (MLS-resistance), which can be either inducible or constitutive. 14-Membered... 

In eukaryotes, only protein synthesis on ribosomes of mitochondria is inhibited. bAffeets only ribosomes in the cytosol. 

Macrolides inhibit growth of bacteria by inhibiting protein synthesis on ribosomes (17,415,416). Bacterial resistance to macrolides is often accompanied by cross-resistance to lincosamide and streptogramin B antibiotics (MLS-resistance), which can be either inducible or constitutive (417). 14-Membered macrolides generally induce resistance to themselves, whereas 16-membered macrolides do not consequendy, one advantage of the latter is their activity against bacteria which are inducibly resistant to erythromycin. Both 14- and 16-membered macrolides lack activity against constitutively resistant strains (387,388). 

By increased (or decreased) synthesis of the enzyme by regulation of transcriptlon/translation/protein synthesis on ribosomes... 

A ribonucleic acid that carries a specific amino acid to the site of protein synthesis on ribosomes. 

Fig. 4.8 Protein synthesis on ribosome. The chemical formulas indicate how the peptide bond is formed (from Cech T (2000) Science 289 878)...

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. 

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. 

One could plunge into the steric problems posed by the mechanism of protein synthesis on the ribosome 25 26)> or consider the steric fit of the hormone insulin to its acceptor in the cell membrane 27>. Or one could delve into the beautiful intricacy of terpenoid, squalene and steroid metabolism, or get lost in double bond formation, or in the steric problems posed by the branched chain fatty acids and their derivatives 28-34). 

Figure 13.3 The process of protein synthesis on the ribosome. The strand of mRNA is shown associated with the small subunit of the ribosome. The aminoacyl-tRNA molecules are shown associated with the large subunit of the ribosome and base-paired with mRNA codons. A peptide bond is in the process of formation between the two associated amino acids, extending the growing polypeptide chain by one unit. On the left, a tRNA is shown leaving the ribosome, having donated its amino acid to the growing chain. On the right, an aminoacyl-tRNA molecule is shown entering the ribosome. It is next in line to contribute its amino acid to that chain.

Figure 29-10 Initiation of protein synthesis on bacterial ribosomes. Images are not drawn to scale. Some details are indicated on the larger scale image at the left.

Dissociable Protein Factors Play Key Roles at the Different Stages in Protein Synthesis on the Ribosome... 

At each stage in protein synthesis on the ribosome—-initiation, elongation, and termination—a different set of protein factors is engaged by the ribosome. Why do such protein factors, which are crucial to the translation, exist separate from the ribosome Why must they cycle on and... 

Termination factors. Proteins that are exclusively involved in the termination reactions of protein synthesis on the ribosome. 

Transfer RNA (tRNA). Any of a family of low-molecular-weight RNAs that transfer amino acids from the cytoplasm to the template for protein synthesis on the ribosome. 

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