In prokaryotes, four elongation factors are required for translation: EF-Tu, EF-Ts, EF-G and EF-P.
EF-Tu mediates the entry of the aminoacyl tRNA into a free site of the ribosome.
EF-Ts serves as the guanine nucleotide exchange factor for EF-Tu, catalyzing the release of GDP from EF-Tu.
EF-G catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation.
EF-P stimulates peptide formation by catalyzing the first synthesis step between the first amino acid (N-formylmethionine) and the second amino acid.