InterPro domain: IPR000178

Initiation factor 2 (IF-2) (gene infB) [ 1 ] is one of the three factorsrequired for the initiation of protein biosynthesis in bacteria. IF-2promotes the GTP-dependent binding of the initiator tRNA to the small subunitof the ribosome. IF-2 is a protein of about 70 to 95 Kd which contains acentral GTP-binding domain flanked by a highly variable N-terminal domain anda more conserved C-terminal domain.Bacterial IF-2 is structurally and functionally related to eukaryoticmitochondrial IF-2 (IF-2(mt)) [ 2 ] as well as to algal and plants chloroplastIF-2 (IF-2(chl)). Both IF-2(mt) and IF-2(chl) are encoded by nuclear genes andare produced as precursor proteins with a transit peptide. An exception arered algae where IF-2(chl) is encoded by the plastid genome [ 3 ].

This model discriminates eubacterial (and mitochondrial) translation initiation factor 2 (IF-2), encoded by the infB gene in bacteria, from similar proteins in the Archaea and Eukaryotes. In the bacteria and in organelles, the initiator tRNA is charged with N-formyl-Met instead of Met. This translation factor acts in delivering the initator tRNA to the ribosome. It is one of a number of GTP-binding translation factors recognised by the pfam HMM GTP_EFTU.

1. Structural and functional domains of E coli initiation factor IF2. Biochimie 73, 1557-66
2. Cloning and sequence analysis of the human mitochondrial translational initiation factor 2 cDNA. J. Biol. Chem. 270, 1859-65
3. Organization of plastid-encoded ATPase genes and flanking regions including homologues of infB and tsf in the thermophilic red alga Galdieria sulphuraria. Plant Mol. Biol. 23, 67-76