EF-G

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Not to be confused with EGF.

EF-G or elongation factor G (historically known as translocase) is one of the prokaryotic elongation factors.

Function[edit]

The factor EF-G catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation. Homologous to EF-Tu + tRNA, EF-G also binds to the ribosome in its GTP-bound state. When it associates with the 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.

Apart from its role in translocation, EF-G, working together with Ribosome Recycling Factor promotes ribosome recycling in a GTP-dependent manner.[1]

Clinical significance[edit]

It is normally inhibited by fusidic acid, but resistance has emerged.[2][3]

Evolution[edit]

EF-G has a complex evolutionary history, with numerous paralogous versions of the factor present in bacteria, suggesting subfunctionalization of different EF-G variants.[4]

References[edit]

  1. ^ 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. doi:10.1016/j.molcel.2005.05.016. PMID 15949442. 
  2. ^ 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. doi:10.1016/j.femsle.2005.05.007. PMID 15935566. 
  3. ^ 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. doi:10.1046/j.1365-2958.2000.01967.x. PMID 10931308. 
  4. ^ 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. doi:10.1093/molbev/msq316. PMID 21097998. 

External links[edit]