Translational elongation factor G: A GTP-driven motor of the ribosome

Institute of Molecular Biology, University of Witten/Herdecke, 58448 Witten, Germany.
Essays in Biochemistry (Impact Factor: 2.84). 02/2000; 35:117-29. DOI: 10.1042/bse0350117
Source: PubMed


EF-G is a large, five-domain GTPase that promotes the directional movement of mRNA and tRNAs on the ribosome in a GTP-dependent manner. Unlike other GTPases, but by analogy to the myosin motor, EF-G performs its function of powering translocation in the GDP-bound form; that is, in a kinetically stable ribosome-EF-G(GDP) complex formed by GTP hydrolysis on the ribosome. The complex undergoes an extensive structural rearrangement, in particular affecting the small ribosomal subunit, which leads to mRNA-tRNA movement. Domain 4, which extends from the 'body' of the EF-G molecule much like a lever arm, appears to be essential for the structural transition to take place. In a hypothetical model, GTP hydrolysis induces a conformational change in the G domain of EF-G which affects the interactions with neighbouring domains within EF-G. The resulting rearrangement of the domains relative to each other generates conformational strain in the ribosome to which EF-G is fixed. Because of structural features of the tRNA-ribosome complex, this conformational strain results in directional tRNA-mRNA movement. The functional parallels between EF-G and motor proteins suggest that EF-G differs from classical G-proteins in that it functions as a force-generating mechanochemical device rather than a conformational switch. There are other multi-domain GTPases that may function in a similar way.

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    • "The expression of the genes associated with protein regulation of this study (EF1a and EF2) was inhibited significantly at 168 h of exposure to Cu 2+ at the two concentrations used. The elongation factor (EF) is one of the protein families with GTPase activity with two main elongation factors (EF1a and EF2), and there are eukaryote cells with multiple and divergent roles in the cellular metabolism affecting mainly the cytoskeleton, peptide synthesis, and protein degradation (Wintermeyer and Rodnina, 2000). In C. gigas exposed to extended thermal stress the expression of EF was strongly down-regulated in gills after 24 days (Meistertzheim et al., 2007). "
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    • "In contrast to this model, another theory proposes that the binding and release of translocase is not simply bringing the activation energy required to catalyse the translocation . Rather, in coupling the free energy of GTP hydrolysis to translocation, EF-G serves as an authentic motor protein and drives the directional movement of transfer and messenger RNAs on the ribosome (Rodnina et al., 1997; Stark et al., 2000; Wintermeyer and Rodnina, 2000). "
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