ENZYME entry: EC

Accepted Name
Protein-synthesizing GTPase.
Alternative Name(s)
Elongation factor (EF).
Initiation factor (IF).
Peptide-release factor (RF).
Peptide-release or termination factor.
Reaction catalysed
GTP + H(2)O <=> GDP + phosphate
  • 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 hydrolyzes it in prokaryotes.
  • In eukaryotes, it is eIF-2 (150 kDa) that binds GTP.
  • In the elongation phase, the GTP-hydrolyzing proteins are the EF-Tu polypeptide of the prokaryotic transfer factor (43 kDa), the eukaryotic elongation factor EF-1-alpha (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-1-alpha catalyze binding of aminoacyl-tRNA to the ribosomal A-site, while EF-G and EF-2 catalyze 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.
  • Formerly EC
PROSITEPDOC00273 ; PDOC00905 ; PDOC00970
PRIAM enzyme-specific profiles3.6.5.3
KEGG Ligand Database for Enzyme Nomenclature3.6.5.3
IUBMB Enzyme Nomenclature3.6.5.3
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