<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>EF2 (or EFG) participates in the elongation phase of protein synthesis by promoting the GTP-dependent translocation of the peptidyl tRNA of the nascent protein chain from the A-site (acceptor site) to the P-site (peptidyl tRNA site) of the ribosome. EF2 also has a role after the termination phase of translation, where, together with the ribosomal recycling factor, it facilitates the release of tRNA and mRNA from the ribosome, and the splitting of the ribosome into two subunits [<cite idref="PUB00014828"/>]. EF2 is folded into five domains, with domains I and II forming the N-terminal block, domains IV and V forming the C-terminal block, and domain III providing the covalently-linked flexible connection between the two. Domains III and V have the same fold (although they are not completely superimposable and domain III lacks some of the superfamily characteristics), consisting of an alpha/beta sandwich with an antiparallel beta-sheet in a (beta/alpha/beta)x2 topology [<cite idref="PUB00011746"/>]. This double split beta/alpha/beta fold is also seen in a number of ribonucleotide binding proteins. It is the most common motif occurring in the translation system and is referred to as the ribonucleoprotein (RNP) or RNA recognition (RRM) motif. </p><p>This domain is found in EF2 proteins from both prokaryotes and eukaryotes, as well as in some tetracycline resistance proteins, peptide chain release factors [<cite idref="PUB00016687"/>], and in the C-terminal region of the bacterial hypothetical protein, YigZ.</p><p>More information about these proteins can be found at Protein of the Month: Elongation Factors [<cite idref="PUB00033962"/>].</p>