Protein synthesis elongation factor

Elongation factors. Protein factors uniquely required during the elongation phase of protein synthesis. Elongation factor G (EF-G) brings about the movement of the peptidyl-tRNA from the A site to the P site of the ribosome. 

GE2270A 394 is an antibiotic produced by Planobispora rosea ATCC 537731. It inhibits Gram-positive bacteria and anaerobes by acting on the protein synthesis elongation factor (EF) <1991JAN693, 1995T4867>. It contains proline, serine, glycine, two thiazolyl amino acids, and a heterocyclic centerpiece of a trisubstituted pyridine, all in a macrocyclic array. 

E. coli membranes contains zinc, which is required for full activity. A functional role for zinc in protein synthesis elongation factor 1 from rat liver has been inferred from the observation that 0.3 mM 1,10-phenanthroline completely abolishes guano-sine 5 -triphosphate binding to EFl there is one zinc per molecule (54 000 Daltons). ... 

Guanosine diphosphate EF-Tu (protein synthesis elongation factor) complex Haemoglobin... 

The third stage of protein synthesis is elongation. Again, our initial focus is on bacterial cells. Elongation requires (1) the initiation complex described above, (2) aminoacyl-tRNAs, (3) a set of three soluble cytosolic proteins called elongation factors (EF-Tu, EF-Ts, and EF-G in bacteria), and (4) GTP. Cells use three steps to add each amino acid residue, and the steps are repeated as many times as there are residues to be added. 

The second phase of protein synthesis is the elongation cycle. This phase begins with the insertion of an aminoacyl-lRKA into the empty A site on the ribosome. The particular species inserted depends on the mRNA codon in the A site. The cognate ami noacyl-tKN A does not simply leave the synthetase and diffuse to the A site. Rather, it is delivered to the A site in association with a 4. Tkd protein called elongation factor Tu (EF-Tu). Elongation factor Tu, another member of the G-protein family, requires GTP to bind aminoacyl-tRNA (Figure 30.23) and to bind the ribosome. The binding of... 

Nilsson L and Nygard O (1986). The mechanism of the protein-synthesis elongation cycle in eukaryotes. Effect of ricin on the ribosomal interaction with elongation factors. Eur J Biochem, 161, 111-117. 

Codon-specific binding of an aminoacyl-tRNA (decoding). The binding of an aminoacyl-tRNA to the A site of the 70S or SOS initiation complex depends upon a protein called elongation factor Tu (EF-Tu or elFl in eukaryotes), which is present as a mixed dimer with a second protein, EF-Ts. In E. coU EF-Ts is a stable 35-kDa protein, while Tu is a 43-kDa soluble protein present in a large excess over Ts. Tu is one of the most abimdant soluble proteins in bacterial cells and accoimts for about 5% of the total protein. Most of the tRNAs in a bacterial cell are present as complexes with Tu. Tu may also have fimctions other than in protein synthesis and is foimd associated with the plasma membrane as well as with ribosomes. 

A different kind of enzyme, translocase [80700-39-6], which transfers a fragment of NAD to the protein—synthesis factor (elongation factor 2), is catalyzed by diphtheria toxin, thereby inhibiting protein synthesis (43). In tumor cells, the rate of protein synthesis is 100 to 1000 times more sensitive to diphtheria toxin than the analogous process in normal cells (41) therefore, diphtheria toxin is selectively toxic to tumor cells. 

Protein synthesis 1 Elongation factor-2 kinase l Translation elongation All cells ... 

Diphtheria toxin, Pseudomonas exotoxin A Elongation factor 2 ADP-ribosylation Inhibition of protein synthesis (diphtheria, Pseudomonas infection)... 

Increased protein synthesis Increased amino acid uptake/increased translation of mRNA Akt-mediated stimulation of system A amino acid transporter and stimulation of mRNA-translation through activation of p70S6kinase and elongation initiation factor 4 (elF4). Possible involvement of atypical PKCs... 

Figure 38-8. Diagrammatic representation of the peptide elongation process of protein synthesis. The small circles labeled n - 1, n, n -I-1, etc, represent the amino acid residues of the newly formed protein molecule. EFIA and EF2 represent elongation factors 1 and 2, respectively. The peptidyl-tRNA and aminoacyl-tRNA sites on the ribosome are represented by P site and A site, respectively.

Shastry, M., Nielsen, J., Ku, T., Hsu, M. J., Liberator, P., Anderson, J., Schmatz, D., and Justice, M. C. (2001). Species-specific inhibition of fungal protein synthesis by sordarin Identification of a sordarin-specificity region in eukaryotic elongation factor 2. Microbiology 147, 383-390. 

A third type of bacterial toxin, diphtheria toxin, catalyzes the ADP-ribosylation of eukaryotic elongation factor (EFTU), a type of small G protein involved in protein synthesis (Table 19-2). The functional activity of the elongation factor is inhibitedby this reaction. Finally, a botulinum toxin ADP-ribosylates and disrupts the function of the small G protein Rho, which appears to be involved in assembly and rearrangement of the actin cytoskeleton (Table 19-2). These toxins maybe involved in neuropathy (see Ch. 36) and membrane trafficking (see Ch. 9). 

Diphtheria causes a demyelinative neuropathy. Coryne-bacterium diphtheriae colonizes the pharynx or open wounds, and secretes a protein exotoxin. The B subunit of this exotoxin binds to plasma membranes and facilitates entry into cytosol of the A subunit, which catalyzes ADP-ribosylation, and inactivation of an elongation factor required for protein synthesis. Cardiac muscle and Schwann cells are particularly susceptible to this toxin, and hence patients with diphtheria develop cardiomyopathy and demyelinative polyneuropathy [20]. While diphtheria is now uncommon because of childhood immunization against C. diphtheriae, the disruption in preventative medicine programs caused by disintegration of the Soviet Union was followed by a substantial incidence of diphtheritic polyneuropathy in Russia. 

DT Corynebacterium AB GTPases Elongation Factor-2 Inhibition of protein synthesis Diphtheria... 

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