After peptide bond formation, this elongation factor of bacteria and organelles catalyzes the translocation of the tRNA-mRNA complex, with its attached nascent polypeptide chain, from the A-site to the P-site of the ribosome. Every completed bacterial genome has at least one copy, but some species have additional EF-G-like proteins. The closest homolog to canonical (e.g. E. coli) EF-G in the spirochetes clusters as if it is derived from mitochondrial forms, while a more distant second copy is also present. Synechocystis PCC6803 has a few proteins more closely related to EF-G than to any other characterized protein. Two of these resemble E. coli EF-G more closely than does the best match from the spirochetes; it may be that both function as authentic EF-G. [Protein synthesis, Translation factors]