IUBMB Enzyme Nomenclature


Accepted name: protein-synthesizing GTPase

Reaction: GTP + H2O = GDP + phosphate

Other name(s): elongation factor (EF); initiation factor (IF); peptide-release or termination factor

Systematic name: GTP phosphohydrolase (mRNA-translation-assisting)

Comments: This enzyme comprises a family of proteins involved in prokaryotic as well as eukaryotic protein synthesis. In the initiation factor complex, it is IF-2b (98 kDa) that binds GTP and subsequently hydrolyses it in prokaryotes. In eukaryotes, it is eIF-2 (150 kDa) that binds GTP. In the elongation phase, the GTP-hydrolysing proteins are the EF-Tu polypeptide of the prokaryotic transfer factor (43 kDa), the eukaryotic elongation factor EF-1α (53 kDa), the prokaryotic EF-G (77 kDa), the eukaryotic EF-2 (70-110 kDa) and the signal recognition particle that play a role in endoplasmic reticulum protein synthesis (325 kDa). EF-Tu and EF-1α catalyse binding of aminoacyl-tRNA to the ribosomal A-site, while EF-G and EF-2 catalyse the translocation of peptidyl-tRNA from the A-site to the P-site. GTPase activity is also involved in polypeptide release from the ribosome with the aid of the pRFs and eRFs.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Kurzchalia, T.V., Bommer, U.A., Babkina, G.T. and Karpova, G.G. GTP interacts with the γ-subunit of eukaryotic initiation factor EIF-2. FEBS Lett. 175 (1984) 313-316. [PMID: 6566615]

2. Kisselev, L.L. and Frolova, L.Yu. Termination of translation in eukaryotes. Biochem. Cell Biol. 73 (1995) 1079-1086. [PMID: 8722024]

3. Rodnina, M.V., Savelsberg, A., Katunin, V.I. and Wintermeyer, W. Hydrolysis of GTP by elongation factor G drives tRNA movement on the ribosome. Nature 385 (1997) 37-41. [PMID: 8985244]

4. Freistroffer, D.V., Pavlov, M.Y., MacDougall, J., Buckingham, R.H. and Ehrenberg, M. Release factor RF3 in E. coli accelerates the dissociation of release factors RF1 and RF2 from the ribosome in a GTP-dependent manner. EMBO J. 16 (1997) 4126-4133. [PMID: 9233821]

5. Krab, I.M. and Parmeggiani, A. EF-Tu, a GTPase odyssey. Biochim. Biophys. Acta 1443, (1998) 1-22. [PMID: 9838020]

[EC created 2000 as EC, transferred 2003 to EC]

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