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Parent Class:

EC-Numbers → 3 -- Hydrolases → 3.6 -- Acting on acid anhydrides → 3.6.5 -- Acting on GTP; involved in cellular and subcellular movement

Synonyms: elongation factor (EF), initiation factor (IF), peptide-release or termination factor

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

Unification Links: BRENDA:3.6.5.3, ENZYME:3.6.5.3, IUBMB-ExplorEnz:3.6.5.3

Supersedes EC number: 3.6.1.48

Reaction:
GTP + H₂O → GDP + phosphate + H⁺

Enzymes and Genes:
ribosome small subunit-dependent GTPase A: rsgA ( Escherichia coli K-12 substr. MG1655 )
ribosome rescue factor HflX: hflX ( Escherichia coli K-12 substr. MG1655 )
50S ribosomal subunit stability factor: der ( Escherichia coli K-12 substr. MG1655 )
selenocysteyl-tRNA-specific translation elongation factor: selB ( Escherichia coli K-12 substr. MG1655 )
30S ribosomal subunit biogenesis factor LepA: lepA ( Escherichia coli K-12 substr. MG1655 )
30S ribosomal subunit maturation GTPase Era: era ( Escherichia coli K-12 substr. MG1655 )
50S ribosomal subunit assembly factor BipA: bipA ( Escherichia coli K-12 substr. MG1655 )

Summary:
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.

Citations: [Kisselev, Kurzchalia84, Rodnina97, Freistroffer97, Krab98]