This family includes the N terminus of eIF-5 P55010 and the C terminus of eIF-2 beta P20042. This region corresponds to the whole of the archaebacterial eIF-2 beta homologue. The region contains a putative zinc binding C4 finger.
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.
Koonin EV; , Protein Sci 1995;4:1608-1617.: Multidomain organization of eukaryotic guanine nucleotide exchange translation initiation factor eIF-2B subunits revealed by analysis of conserved sequence motifs. PUBMED:8520487 EPMC:8520487.