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Literature summary extracted from

  • Eiler, D.; Lin, J.; Simonetti, A.; Klaholz, B.P.; Steitz, T.A.
    Initiation factor 2 crystal structure reveals a different domain organization from eukaryotic initiation factor 5B and mechanism among translational GTPases (2013), Proc. Natl. Acad. Sci. USA, 110, 15662-15667.
    View publication on PubMedView publication on EuropePMC

Cloned(Commentary)

EC Number Cloned (Comment) Organism
3.6.5.3 recombinant expression in Escherichia coli strain BL21(DE3) Thermus thermophilus

Crystallization (Commentary)

EC Number Crystallization (Comment) Organism
3.6.5.3 purified recombinant apo-enzyme IF2 and its complex with GDP, vapor diffusion, mixing of 25 mg/ml protein in 30 mM HEPES-KOH, pH 7.5, 10 mM MgCl2, 30 mM NH4Cl, 1 mM EDTA NaOH, and 1 mM 2-mercaptoethanol in a 4:1 ratio with a well solution contaning 0.1 M calcium acetate, 0.04 M Na-cacodylate, pH 5.4, 8% w/v PEG 8000, 10-30 mM glycl-glycine, and 10-30 mM taurine, 2 weeks, X-ray diffraction structure determination and analysis aat 3.09 A resolution Thermus thermophilus

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
3.6.5.3 Mg2+ required Thermus thermophilus

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
3.6.5.3 GTP + H2O Thermus thermophilus
-
 GDP + phosphate
-
 ?
3.6.5.3 GTP + H2O Thermus thermophilus HB8 / ATCC 27634 / DSM 579
-
 GDP + phosphate
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
3.6.5.3 Thermus thermophilus P48515
-
-
3.6.5.3 Thermus thermophilus HB8 / ATCC 27634 / DSM 579 P48515
-
-

Purification (Commentary)

EC Number Purification (Comment) Organism
3.6.5.3 recombinant enzyme from Escherichia coli by heat treatment at 65°C for 20 min, ultracentrifugation, hydrophobic interaction chromatography, gel filtration, and ultrafiltration Thermus thermophilus

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
3.6.5.3 GTP + H2O
-
 Thermus thermophilus GDP + phosphate
-
 ?
3.6.5.3 GTP + H2O
-
 Thermus thermophilus GDP + phosphate GDP binding structure analysis ?
3.6.5.3 GTP + H2O
-
 Thermus thermophilus HB8 / ATCC 27634 / DSM 579 GDP + phosphate
-
 ?
3.6.5.3 GTP + H2O
-
 Thermus thermophilus HB8 / ATCC 27634 / DSM 579 GDP + phosphate GDP binding structure analysis ?

Subunits

EC Number Subunits Comment Organism
3.6.5.3 More three-dimensional structure organization of the enzyme, overview Thermus thermophilus

Synonyms

EC Number Synonyms Comment Organism
3.6.5.3 IF2
-
 Thermus thermophilus
3.6.5.3 initiation factor 2
-
 Thermus thermophilus

Cofactor

EC Number Cofactor Comment Organism Structure
3.6.5.3 additional information enzyme IF2 does not have an identified nucleotide exchange factor Thermus thermophilus

General Information

EC Number General Information Comment Organism
3.6.5.3 evolution unlike all other translational GTPases, the enzyme does not have an effecter domain that stably contacts the switch II region of the GTPase domain. The domain organization of enzyme IF2 is inconsistent with the articulated lever mechanism of communication between the GTPase and initiator tRNA binding domains that is proposed for the eukaryotic initiation factor 5B, eIF5B. The catalytic mechanism of enzyme IF2 appears to be unique among the translational GTPases of prokaryotes. Because the interaction of enzyme IF2 and initiator tRNA is strongest in the presence of the 30S ribosomal subunit, it is not GDP or GTP but the 30S ribosomal subunit that facilitates IF2 to interact with the initiator tRNA Thermus thermophilus
3.6.5.3 additional information comparison of crystal structures of prokaryotic initiation factor 2, IF2, from Thermus thermophilus with eukaryotic initiation factor 5B, eIF5B from Methanobacterium thermoautotrophicum, structure homology modeling, overview. The structures are significantly different. Enzyme IF2 is not a classical GTPase and acts more as a conformational switch, although IF2 is not a conformational switch like EF-G and RF3 are proposed to be. Enzyme IF2 functions better with GTP but does not require it, and IF2 does not have an identified nucleotide exchange factor. Comparison of switch II regions of translational GTPases Thermus thermophilus
3.6.5.3 physiological function the enzyme, initiation factor 2, is a GTPase that positions the initiator tRNA on the 30S ribosomal initiation complex and stimulates its assembly to the 50S ribosomal subunit to make the 70S ribosome Thermus thermophilus