Initiation factor 2 (IF-2) (gene infB) [<cite idref="PUB00000691"/>] 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)) [<cite idref="PUB00002916"/>] 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 [<cite idref="PUB00004567"/>].<p> 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. </p>