Elongation factors

From Palaeos

During translation of mRNA on ribosomes, each tRNA binds successively to three sites on the ribosome: the A (acceptor) site, the P (peptide site), and the E (exit) site. Elongation factors are small, GTP-dependant proteins which are instrumental in this process. EF-Tu (bacteria) or EF-1α (eukaryotes) binds the tRNA into the A site. After the amino acid on the tRNA has been added to the growing peptide chain, EF-G (bacteria) or EF-2 (eukaryotes) is responsible for moving the peptidyl-tRNA complex to the P site. EF-Tu and EF-G are themselves believed to be homologous. That is, they share sequences which suggest that the genes coding for these proteins derived from a single common ancestral gene, probably before LUCA. The operation of elongation factors is described in a bit more detail in the figure at tRNA.