InterPro domain: IPR016189

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 [ 1 ]. 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 [ 2 ]. 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 [ 3 ]. 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 [ 4 ]. IF5 interacts directly with IF1, IF2beta and IF3c, which together with IF2-bound Met-tRNA(i)(Met) form the MFC.

This superfamily represents the N-terminal alpha/beta domain found in IF2beta and IF5.

1. Structure of the beta subunit of translation initiation factor 2 from the archaeon Methanococcus jannaschii: a representative of the eIF2beta/eIF5 family of proteins. Biochemistry 41, 5730-42
2. Structure of the archaeal translation initiation factor aIF2 beta from Methanobacterium thermoautotrophicum: implications for translation initiation. Protein Sci. 13, 659-67
3. Functional analysis of the translation factor aIF2/5B in the thermophilic archaeon Sulfolobus solfataricus. Mol. Microbiol. 65, 700-13
4. The crystal structure of the carboxy-terminal domain of human translation initiation factor eIF5. J. Mol. Biol. 360, 457-65