<p> A beta barrel of circularly permuted topology is found in many transcription proteins, including initiation and elongation factors, and also some ribosomal proteins, although in these cases the fold is elaborated with additional structures. The beta barrel domain is represented by domain 2 of the elongation factors EF-Tu [<cite idref="PUB00011834"/>] and eEF1A [<cite idref="PUB00011832"/>], both of which function to recognise and transport aminoacyl-tRNA to the acceptor (A) site of the ribosome during the elongation process, and of EF-G [<cite idref="PUB00011746"/>], which functions in translocating the peptidyl tRNA from the A site to the peptidyl (P) site. This domain is also present in initiation factors, in domain 2 of eIF2 gamma subunit [<cite idref="PUB00011835"/>], and domains 2 and 4 of IF2/eIF5B [<cite idref="PUB00011836"/>], both of which function to transport the initiator methionyl-tRNA to the ribosome. This beta barrel domain may be involved in interactions with the switch 2 region to stabilise the relative orientations of the domains, which undergo functionally important conformational changes between GTP- and GDP-bound states.</p><p>More information about translation elongation factors can be found at Protein of the Month: Elongation Factors [<cite idref="PUB00033962"/>].</p> Translation elongation/initiation factor/Ribosomal, beta-barrel