EF-G

EF-G or elongation factor G (historically known as translocase) is a prokaryotic elongation factor and a GTPase responsible for catalyzing the coordinated movement of tRNA and mRNA through the ribosome.[1]

Function

The factor EF-G catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation.[1] Just like the EF-Tu+tRNA+GTP complex, EF-G binds to the ribosome in its GTP-bound state. When it binds to the ribosome A-site, EF-G causes the tRNA previously occupying that site to occupy an intermediate A/P position (bound to the A site of the small ribosomal subunit and to the P site of the large subunit), and the tRNA in the P site is shifted to a P/E hybrid state. EF-G hydrolysis of GTP causes a conformation change that forces the A/P tRNA to fully occupy the P site, the P/E tRNA to fully occupy the E site (and exit the ribosome complex), and the mRNA to shift three nucleotides down relative to the ribosome due to its association with these tRNA molecules. The GDP-bound EF-G molecule then dissociates from the complex, leaving another free A-site where the elongation cycle can start again.[1][2]

Apart from its role in translocation, EF-G, working together with Ribosome Recycling Factor, promotes ribosome recycling in a GTP-dependent manner.[3]

Clinical significance

It is normally inhibited by fusidic acid, but resistance has emerged.[4][5]

Evolution

EF-G has a complex evolutionary history, with numerous paralogous versions of the factor present in bacteria, suggesting subfunctionalization of different EF-G variants.[6]

References

  1. 1 2 3 Shoji, S; Walker, SE; Fredrick, K (2009). "Ribosomal translocation: one step closer to the molecular mechanism". ACS Chem Biol. 4: 93–107. PMC 3010847 Freely accessible. PMID 19173642. doi:10.1021/cb8002946.
  2. ↑ da Cunha, CE; Belardinelli, R; Peske, F; Holtkamp, W; Wintermeyer, W; Rodnina, MV (2013). "Dual use of GTP hydrolysis by elongation factor G on the ribosome". Translation. 1: e24315. doi:10.4161/trla.24315.
  3. ↑ Zavialov AV, Hauryliuk VV, Ehrenberg M (2005). "Splitting of the posttermination ribosome into subunits by the concerted action of RRF and EF-G". Molecular Cell. 18 (6): 675–686. PMID 15949442. doi:10.1016/j.molcel.2005.05.016.
  4. ↑ Macvanin M, Hughes D (June 2005). "Hyper-susceptibility of a fusidic acid-resistant mutant of Salmonella to different classes of antibiotics". FEMS microbiology letters. 247 (2): 215–20. PMID 15935566. doi:10.1016/j.femsle.2005.05.007.
  5. ↑ Macvanin M, Johanson U, Ehrenberg M, Hughes D (July 2000). "Fusidic acid-resistant EF-G perturbs the accumulation of ppGpp". Molecular Microbiology. 37 (1): 98–107. PMID 10931308. doi:10.1046/j.1365-2958.2000.01967.x.
  6. ↑ G C Atkinson; S L Baldauf (2011). "Evolution of elongation factor G and the origins of mitochondrial and chloroplast forms". Molecular Biology and Evolution. 28 (3): 1281–92. PMID 21097998. doi:10.1093/molbev/msq316.
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