Elongation factors domain structure

The general topology of rubredoxins is also observed in the general zinc-ribbon motif in RNA polymerases or in transcription factors (59). The first published zinc-ribbon structure was that of the nucleic-acid binding domain of human transcriptional elongation factor TFIIS (PDB file ITFI) 40). These zinc binding domains and rubredoxins... 

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. 

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... 

Figure 29.28. Structure of Elongation Factor Tu. The structure of a complex between elongation factor Tu (EF-Tu) and an aminoacyl-tRNA. The amino-terminal domain of EF-Tu is a P-loop NTPase domain similar to those in other G proteins. 

Figure 29.29. Molecular Mimicry. The structure of elongation factor G (EF-G) is remarkably similar in shape to that of the EF-Tu-tRNA complex (see Figure 29,28). The amino-terminal region of EF-G is homologous to EF-Tu, and the carboxyl-terminal region (shown in red) comprises a set of protein domains that adopted the shape of a tRNA molecule over the course of evolution.

Three-dimensional structures. The structure of the GTP-binding domain of elongation factor EF-Tu was determined by Jumak in 1985 and that of the complete three-domain structure later.When the structure of the catalytic domain of the first Ras protein was determined (Fig. 11-7A) it was clear that it was similar to that of EF-Tu. ° The same was true for the transducin for the inhibitory... 

The mechanisms by which several of the translational factors act in protein synthesis have been suggested based on detailed structural analyses. Elongation factor Tu was the first factor for which an X-ray crystallographic structure was determined, and was also the first GTP-binding protein whose structure was elucidated. This protein is organized in three structural domains. Domain 1 is the GTP-binding domain (G-domain) consisting of a nucleotide... 

When the crystal structure of EF-G GDP was solved, it revealed a surprising and elegant structural feature. Elongation factor G consists of five structural domains, and from sequence comparisons Domains 1 and 2 were expected to be similar in conformation to EF-Tu Domains 1 and 2. This conformational mimic does indeed occur. Domains 3 and 5 of EF-G contain protein folds similar to some ribosomal proteins whose structures are known, while Domain 4 adopts an unusual fold. This domain is elongated and points away from the rest of the protein. 

FIGURE 10 Comparison of elongation factor structures. The crystal structures of the EF-Tu GDPNP tRNA ternary complex (left) and EF-G (right) revealed that Domains 3, 4, and 5 of EF-G mimic the conformation of EF-Tu-bound tRNA. Several other translational factors have been determined or predicted to similarly mimic the tRNA structure. 

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