<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 EF1B (also known as EF-Ts or EF-1beta/gamma/delta) is a nucleotide exchange factor that is required to regenerate EF1A from its inactive form (EF1A-GDP) to its active form (EF1A-GTP). EF1A is then ready to interact with a new aminoacyl-tRNA to begin the cycle again. EF1B is more complex in eukaryotes than in bacteria, and can consist of three subunits: EF1B-alpha (or EF-1beta), EF1B-gamma (or EF-1gamma) and EF1B-beta (or EF-1delta) [<cite idref="PUB00033953"/>].</p><p>This entry represents the C-terminal region of the beta (EF-1beta or EF1B-alpha) and delta (EF-1delta or EF1B-beta) chains of EF1B proteins from eukaryotes and archaea. The beta and delta chains have exchange activity, which mainly resides in their homologous C-terminal regions. Their N-terminal regions may be involved in interactions with the gamma chain (EF-1gamma).</p><p>More information about these proteins can be found at Protein of the Month: Elongation Factors [<cite idref="PUB00033962"/>].</p>