G elongation factor

Elongation Functional 70 S ribosomes aminoacyl-tRNAs GTP, Mg2+, EF-Tu, EF-Ts, and EF-G elongation factors Functional 80 S ribosomes aminoacyl-tRNAs GTP, Mg2+, EF-1, EF-1, and EF-2 elongation factors... 

Abbreviations used aa-tRNA, aminoacyl-tRNA pep-tRNA, peptidyl-tRNA BrAcPhe-tRNA, AT-bromoacetyl-Phe-tRNA BrAcMet-tRNA, N-bromoacetyl-Met-tRNA, 6-BrAcLys-tRNA, JV -bromoacetyl-Lys-tRNA EF-T , elongation factor T EF-G, elongation factor G GMPPNP, guanylyl-imidodiphosphate. 

Wang, L., and Proud, C. G. (2002b). Regulation of the phosphorylation of elongation factor 2 by MEK-dependent signaling in adult rat cardiomyocytes. FEBS Lett. 531, 285—289. 

Skold, S.-E. (1983) Chemical crosslinking of elongation factor G to the 23S RNA in 70S ribosomes from Escherichia coli. Nucleic Acids Res. 11, 4923. 

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). 

EFTU eukaryotic elongation factor GRK G protein receptor kinase... 

Orphanides, G., Wu, W.H., Lane, W.S., Hampsey, M., and Reinberg, D. (1999) The chromatin-specific transcription elongation factor FACT comprises human SPT16 and SSRPl proteins. Nature 400, 284-288. 

Simic, R., Lindstrom, D.L., Tran, H.G., Roinick, K.L., Costa, P.J., Johnson, A.D., Hartzog, G.A., and Arndt, K.M. (2003) Chromatin remodeling protein Chdl interacts with transcription elongation factors and localizes to transcribed genes. EMBO J. 22, 1846-1856. 

Ribosome recycling factor (RRF) and elongation factor-G (EF-G) are required to recycle the prokaryotic ribosome back to a new round of initiation after termination (Nakamura and Ito 2003). No recycling factor has been identified so far in the cytoplasm of eukaryotic cells. To explain this difference it has been postulated that eukaryotic eRF3 has a dual function ... 

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).

The superfamily of GTPases with their more than hundred members are divided by sequence homologies, molecular weight and subimit structure into further (super)fa-milies. These are the families of the heterotrimeric G-proteins, the Ras/GTPase superfamily and the family of initiation and elongation factors (Fig. 5.13). 

Highly potent bacterial toxins such as ricin and diphtheria can completely inhibit cellular protein synthesis at very low levels [26]. The bacterial toxin exerts cytotoxicity through enzymatic inactivation of factors essential for protein synthesis (e.g., riboso-mal RNA, elongation factor 2 or EF2). Inactivation of these proteins, which are... 

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. 

Monomeric G proteins. An entirely different class of G proteins was discovered when it was found that the small 189-residue, 21-kDa protein products of the human oncogenes and proto-oncogenes known as ras are monomeric G proteins.186 197-200 There are over 80 related proteins of this group of nine families.2003 They include the much larger elongation factor EF-Tu, which functions in protein synthesis (Chapter 29). 

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