<p>Translation elongation factors are responsible for two main processes during protein synthesis on the ribosome [<cite idref="PUB00033953"/>, <cite idref="PUB00033952"/>, <cite idref="PUB00033951"/>]. EF1A (or EF-Tu) is responsible for the selection and binding of the cognate aminoacyl-tRNA to the A-site (acceptor site) of the ribosome. EF2 (or EF-G) is responsible for the translocation of the peptidyl-tRNA from the A-site to the P-site (peptidyl-tRNA site) of the ribosome, thereby freeing the A-site for the next aminoacyl-tRNA to bind. Elongation factors are responsible for achieving accuracy of translation and both EF1A and EF2 are remarkably conserved throughout evolution.</p><p>Elongation factor EF2 (EF-G) is a G-protein. It brings about the translocation of peptidyl-tRNA and mRNA through a ratchet-like mechanism: the binding of GTP-EF2 to the ribosome causes a counter-clockwise rotation in the small ribosomal subunit; the hydrolysis of GTP to GDP by EF2 and the subsequent release of EF2 causes a clockwise rotation of the small subunit back to the starting position [<cite idref="PUB00033958"/>, <cite idref="PUB00033959"/>]. This twisting action destabilises tRNA-ribosome interactions, freeing the tRNA to translocate along the ribosome upon GTP-hydrolysis by EF2. EF2 binding also affects the entry and exit channel openings for the mRNA, widening it when bound to enable the mRNA to translocate along the ribosome.</p><p>This entry represents archaeal EF2 proteins (also known as aEF2), which are more similar to eukaryotic EF2 than to bacterial EF2 (or EFG), both in sequence similarity and in sharing with eukaryotes the property of having a diphthamide (modified His) residue at a conserved position. The diphthamide can be ADP-ribosylated by diphtheria toxin in the presence of NAD.</p><p>More information about these proteins can be found at Protein of the Month: Elongation Factors [<cite idref="PUB00033962"/>].</p> Translation elongation factor EFG/EF2, archaeal