eIF2B_5

domain present in translation initiation factor eIF2B and eIF5

• SMART accession number: SM00653
• Interpro abstract (IPR002735):

  The beta subunit of archaeal and eukaryotic translation initiation factor 2 (IF2beta) and the N-terminal domain of translation initiation factor 5 (IF5) show significant sequence homology [(PUBMED:11980477)]. Archaeal IF2beta contains two independent structural domains: an N-terminal mixed alpha/beta core domain (topological similarity to the common core of ribosomal proteins L23 and L15e), and a C-terminal domain consisting of a zinc-binding C4 finger [(PUBMED:14978306)]. Archaeal IF2beta is a ribosome-dependent GTPase that stimulates the binding of initiator Met-tRNA(i)(Met) to the ribosomes, even in the absence of other factors [(PUBMED:17608795)]. The C-terminal domain of eukaryotic IF5 is involved in the formation of the multi-factor complex (MFC), an important intermediate for the 43S pre-initiation complex assembly [(PUBMED:16781736)]. IF5 interacts directly with IF1, IF2beta and IF3c, which together with IF2-bound Met-tRNA(i)(Met) form the MFC.

  This entry represents both the N-terminal and zinc-binding domains of IF2, as well as a domain in IF5.

• GO process: translational initiation (GO:0006413)
• GO function: translation initiation factor activity (GO:0003743)

There are 334 eIF2B_5 domains in 333 proteins in SMART's nrdb database.

Cellular role (predicted cellular role)

Cellular role: translation
Binding / catalysis: RNA

Literature (relevant references for this domain)

Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

• Koonin EV
• Multidomain organization of eukaryotic guanine nucleotide exchange translation initiation factor eIF-2B subunits revealed by analysis of conserved sequence motifs.
• Protein Sci. 1995; 4: 1608-17

Computer-assisted analysis of amino acid sequences using methods for database screening with individual sequences and with multiple alignment blocks reveals a complex multidomain organization of yeast proteins GCD6 and GCD1, and mammalian homolog of GCD6-subunits of the eukaryotic translation initiation factor eIF-2B involved in GDP/GTP exchange on eIF-2. It is shown that these proteins contain a putative nucleotide-binding domain related to a variety of nucleotidyltransferases, most of which are involved in nucleoside diphosphate-sugar formation in bacteria. Three conserved motifs, one of which appears to be a variant of the phosphate-binding site (P-loop) and another that may be considered a specific version of the Mg(2+)-binding site of NTP-utilizing enzymes, were identified in the nucleotidyltransferase-related domain. Together with the third unique motif adjacent to the the P-loop, these motifs comprise the signature of a new superfamily of nucleotide-binding domains. A domain consisting of hexapeptide amino acid repeats with a periodic distribution of bulky hydrophobic residues (isoleucine patch), which previously have been identified in bacterial acetyltransferases, is located toward the C-terminus from the nucleotidyltransferase-related domain. Finally, at the very C-termini of GCD6, eIF-2B epsilon, and two other eukaryotic translation initiation factors, eIF-4 gamma and eIF-5, there is a previously undetected, conserved domain. It is hypothesized that the nucleotidyltransferase-related domain is directly involved in the GDP/GTP exchange, whereas the C-terminal conserved domain may be involved in the interaction of eIF-2B, eIF-4 gamma, and eIF-5 with eIF-2.

Structure (3D structures containing this domain)

3D Structures of eIF2B_5 domains in PDB

PDB code	Title
1k8b	Nmr structure analysis of the n-terminal domain of archaeal translation initiation factor 2 subunit beta
1nee	Structure of archaeal translation factor aif2beta from methanobacterium thermoautrophicum
2d74	Crystal structure of translation initiation factor aif2betagamma heterodimer
2dcu	Crystal structure of translation initiation factor aif2betagamma heterodimer with gdp
2e9h	Solution structure of the eif-5_eif-2b domain from human eukaryotic translation initiation factor 5
2g2k	Nmr structure of an n-terminal fragment of the eukaryotic initiation factor 5 (eif5)
2nxu	Atomic structure of translation initiation factor aif2 beta- subunit from archaebacteria sulfolobus solfataricus: high resolution nmr in solution
2qmu	Structure of an archaeal heterotrimeric initiation factor 2 reveals a nucleotide state between the gtp and the gdp states
3cw2	Crystal structure of the intact archaeal translation initiation factor 2 from sulfolobus solfataricus .

Links (links to other resources describing this domain)

• PFAM: eIF5_eIF2B
• INTERPRO: IPR002735