Translation elongation factor EFG/EF2 (IPR004540)

Short name: Transl_elong_EFG/EF2

Overlapping homologous superfamilies

Family relationships


Translation elongation factors are responsible for two main processes during protein synthesis on the ribosome [PMID: 12762045, PMID: 15922593, PMID: 12932732]. 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.

EF-G is a large, five-domain GTPase that promotes the directional movement of mRNA and tRNAs on the ribosome in a GTP-dependent manner. Unlike other GTPases, but by analogy to the myosin motor, EF-G performs its function of powering translocation in the GDP-bound form; that is, in a kinetically stable ribosome-EF-G(GDP) complex formed by GTP hydrolysis on the ribosome. The complex undergoes an extensive structural rearrangement, in particular affecting the small ribosomal subunit, which leads to mRNA-tRNA movement. Domain 4, which extends from the 'body' of the EF-G molecule much like a lever arm, appears to be essential for the structural transition to take place. In a hypothetical model, GTP hydrolysis induces a conformational change in the G domain of EF-G, which affects the interactions with neighbouring domains within EF-G. The resulting rearrangement of the domains relative to each other generates conformational strain in the ribosome to which EF-G is fixed. Because of structural features of the tRNA-ribosome complex, this conformational strain results in directional tRNA-mRNA movement. The functional parallels between EF-G and motor proteins suggest that EF-G differs from classical G-proteins in that it functions as a force-generating mechanochemical device rather than a conformational switch [PMID: 12471894].

Every completed bacterial genome has at least one copy, but some species have additional EF-G-like proteins. The closest homologue to canonical (e.g. Escherichia coli) EF-G in the spirochetes clusters as if it is derived from mitochondrial forms, while a more distant second copy is also present. Synechocystis sp. (strain PCC 6803) has a few proteins more closely related to EF-G than to any other characterised protein. Two of these resemble E. coli EF-G more closely than does the best match from the spirochetes; it may be that both function as authentic EF-G.

GO terms

Biological Process

GO:0006414 translational elongation

Molecular Function

GO:0005525 GTP binding
GO:0003746 translation elongation factor activity

Cellular Component

GO:0005622 intracellular

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.