Tu elongation factor

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... 

This prevents further ineorporation of aminoaeyl-tRNA by bloeking the binding of EF-Tu GTP. Like the tetraeyelines, fusidie aeid owes its seleetive antimierobial aetion to active uptake by bacteria and exclusion fiom manunalian cells. The equivalent elongation factor in mammalian cells, EF-2 is susceptible to fusidie acid in cell-free systems. 

The electron microscope (EM) has been used extensively in molecular biological research (1). Among its many applications, EM has been used to visualize polyribosomal structure (2), to visualize ribosome substructure (3), and to visualize the elongation factor Tu on the Escherichia... 

StarkH, RodninaM, Rinke-Appel J, BrimacombeR, WintermeyerW, vanHeelM. Visualization of elongation factor Tu on the Escherichia coli ribosome. Nature 1997 389 403 105. 

EFTsNT A UBA-like domain with a clear role outside of ubiquitin binding is found at the N-terminus of EF-Ts proteins. The relationship of this region to genuine UBA domains is well established as there is a structure of full-length EF-Ts available [67]. Nevertheless, this domain is widespread in bacteria and archaea, which obviously lack a proper ubiquitin system. The physiological role of the EFTsNT domain is rather in the binding to the elongation factor EF-Tu, which has no resemblance to ubiquitin. 

In addition to the ribosomal proteins, the two initiation factors IF-1 (Pon et ai, 1979) and IF-3 (Brauer and Wittmann-Liebold, 1978), the elongation factor EF-Tu (Arai et ai, 1980), and the two proteins NS-1 and NS-2 (Mende et ai, 1978), which bind to ribosomes and to DNA, have been completely sequenced (Table III). 

Upon being formed by the aaRSs, aa-tRNAs are trapped by the elongation factor EF-Tu in prokaryotes and EF-IA in eukaryotes and archaea and carried to the ribosome where they are used for elongation of the... 

The trCCR experiment has been apphed to study the boimd conformation of a nucleotide analog bound to Elongation Factor Tu [8,23]. Measurements of the CCR-rates /hi ci C2 H2 and /h3 c3 C4 H4 of the C-labelled nucleotide in the presence of its receptor, resulted in an unambiguous determination of the sugar conformation of the nucleotide. 

Kothe, U. Rodnina, M. V. Delayed Release of Inorganic Phosphate from Elongation Factor Tu Following GTP Hydrolysis on the Ribosome. Biochemistry 2006, 45, 12767-12774. 

Fig. 5.12. Structure of the G-domain of the elongation factor EF-Tu from T. ther-mophilus with bonnd GppNHp, according to Berchthold et al., (1993). The non-hydrolysable analog GppNHp, the P loop and the switch regions I and II are shown, which play an important role in transition from the inactive GDP form to the active GTP form (see also 5.5.6 and 9.2.1). MOLSKRIPT representation according to Kranhs, (1991).

Berchthold, H., Reshetnikova, L., Reiser, C.O.A., Schirmer, N.K., Sprinzl, M. and Hilgenfeld, R. Crystal structure of active elongation factor Tu reveals major domain rearrangements (1993) Nature 365,126-132... 

One subunit (Mr 65,000) is the product of the replicase gene encoded by the viral RNA and has the active site for replication. The other three subunits are host proteins normally involved in host-cell protein synthesis the E. coli elongation factors Tu (Mt 30,000) and Ts (Mr 45,000)... 

Functional 70S ribosome (initiation complex) Aminoacyl-tRNAs specified by codons Elongation factors (EF-Tu, EF-Ts, EF-G)... 

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 elongation cycle in eukaryotes is quite similar to that in prokaryotes. Three eukaryotic elongation factors (eEFla, eEFljSy, and eEF2) have functions analogous to those of the bacterial elongation factors (EF-Tu, EF-Ts, and EF-G, respectively). Eukaryotic ribosomes do not have an E site uncharged tRNAs are expelled directly from the P site. 

Sprinzl, M. (1994) Elongation factor Tu a regulatory GTPase with an integrated effector. Trends Biochem. Sci. 19, 245-250. 

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