EFG_mtEFG1_IV: domains similar to domain IV of the bacterial translational elongation factor (EF) EF-G. Included in this group is a domain of mitochondrial Elongation factor G1 (mtEFG1) proteins homologous to domain IV of EF-G. Eukaryotic cells harbor 2 protein synthesis systems: one localized in the cytoplasm, the other in the mitochondria. Most factors regulating mitochondrial protein synthesis are encoded by nuclear genes, translated in the cytoplasm, and then transported to the mitochondria. The eukaryotic system of elongation factor (EF) components is more complex than that in prokaryotes, with both cytoplasmic and mitochondrial elongation factors and multiple isoforms being expressed in certain species. During the process of peptide synthesis and tRNA site changes, the ribosome is moved along the mRNA a distance equal to one codon with the addition of each amino acid. In bacteria this translocation step is catalyzed by EF-G_GTP, which is hydrolyzed to provide the required energy. Thus, this action releases the uncharged tRNA from the P site and transfers the newly formed peptidyl-tRNA from the A site to the P site. Eukaryotic mtEFG1 proteins show significant homology to bacterial EF-Gs. Mutants in yeast mtEFG1 have impaired mitochondrial protein synthesis, respiratory defects and a tendency to lose mitochondrial DNA. There are two forms of mtEFG present in mammals (designated mtEFG1s and mtEFG2s) mtEFG2s are not present in this group.
Jiyao W et al.(2023). "The conserved domain database in 2023.",