1VB5: Crystal Structure Analysis Of The Pyrococcus Horikoshii Ot3 Translation Initiation Factor Eif-2b

Eukaryotic translation initiation factor 2B (eIF2B) is the guanine-nucleotide exchange factor for eukaryotic initiation factor 2 (eIF2). eIF2B is a heteropentameric protein composed of alpha- subunits. The alpha, beta, and delta subunits form a regulatory subcomplex, while the gamma and form a catalytic subcomplex. Archaea possess homologues of alpha, beta, and delta subunits of eIF2B. Here, we report the three-dimensional structure of an archaeal regulatory subunit (aIF2Balpha) from the hyperthermophilic archaeon Pyrococcus horikoshii OT3 determined by X-ray crystallography at 2.2A resolution. aIF2Balpha consists of two subdomains, an N-domain (residues 1-95) and a C-domain (residues 96-276), connected by a long alpha-helix (alpha5: 78-106). The N-domain contains a five helix bundle structure, while the C-domain folds into the alpha/beta structure, thus showing similarity to D-ribose-5-phosphate isomerase structure. The presence of two molecules in the crystallographic asymmetric unit and the gel filtration analysis suggest a dimeric structure of aIF2Balpha in solution, interacting with each other by C-domains. Furthermore, the crystallographic 3-fold symmetry generates a homohexameric structure of aIF2Balpha; the interaction is primarily mediated by the long alpha-helix at the N-domains. This structure suggests an architecture of the three subunits, alpha, beta, and delta, in the regulatory subcomplex within eIF2B.
PDB ID: 1VB5Download
MMDB ID: 30980
PDB Deposition Date: 2004/2/22
Updated in MMDB: 2012/12
Experimental Method:
x-ray diffraction
Resolution: 2.2  Å
Source Organism:
Similar Structures:
Biological Unit for 1VB5: dimeric; determined by author and by software (PISA)
Molecular Components in 1VB5
Label Count Molecule
Proteins (2 molecules)
Translation Initiation Factor Eif-2b
Molecule annotation
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Citing MMDB