EF-G

EF-G (elongation factor G) is a protein that plays a crucial role in the elongation phase of protein synthesis. It is found in all bacteria, archaea, and eukaryotes. EF-G is responsible for the translocation of the tRNA and mRNA down the ribosome at the end of each round of peptide bond formation.

Structure

EF-G is a large protein, composed of five domains. The first three domains (G, II, and III) are similar in structure to the GTPase domain and the two GTP binding domains of EF-Tu. Domains IV and V are unique to EF-G and are responsible for its specific functions in translocation.

Function

EF-G's primary role is in the translocation of tRNA and mRNA down the ribosome. This occurs after the formation of a peptide bond in the peptidyl transferase center of the ribosome. EF-G, bound to GTP, binds to the ribosome, causing a conformational change that allows for the movement of the tRNA and mRNA. The GTP is then hydrolyzed and EF-G is released.

EF-G also plays a role in the process of ribosome recycling, the disassembly of the 70S ribosome into its 50S and 30S subunits at the end of translation.

Inhibition

Several antibiotics inhibit the function of EF-G. These include fusidic acid, which prevents the release of EF-G from the ribosome after GTP hydrolysis, and the aminoglycosides, which appear to inhibit the binding of EF-G to the ribosome.

See also

• Elongation factor
• Translation (biology)
• Ribosome

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  EF-G, mRNA, and tRNAs in POST state PDB 4W29
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  EF-G and tRNAs in the POST state