The factor EF-G catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation. 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.
Apart from its role in translocation, EF-G, working together with Ribosome Recycling Factor, promotes ribosome recycling in a GTP-dependent manner.
^Zavialov AV, Hauryliuk VV, Ehrenberg M. (2005). "Splitting of the posttermination ribosome into subunits by the concerted action of RRF and EF-G". Molecular Cell18 (6): 675–686. doi:10.1016/j.molcel.2005.05.016. PMID15949442.
^G C Atkinson, S L Baldauf (2011). "Evolution of elongation factor G and the origins of mitochondrial and chloroplast forms". Molecular Biology and Evolution28 (3): 1281–92. doi:10.1093/molbev/msq316. PMID21097998.