InterPro domain: IPR015256

This entry represents the C-terminal domain of the gamma subunit of eukaryotic translation initiation factor 2 (eIF2-gamma) found in Eukaryota and Archaea. This domain has a beta barrel structure with Greek key topology. It is required for formation of the ternary complex with GTP and initiator tRNA [ 1 ].

In eukaryotes and archaea, the e/aIF2 factor is involved in the initiation of protein biosynthesis. In its GTP bound form, e/aIF2 delivers methionylated initiator tRNA to the small subunit of the ribosome. After the pairing between the AUG initiation codon on mRNA and the CAU anticodon of the initiator tRNA, GTP is hydrolysed and e/aIF2:GDP is released from the ribosome. In eukaryotes, eIF2B acts as the guanine nucleotide exchange factor for eIF2. Archaea have no equivalent of eIF2B, and the exchange between GDP and GTP is thought to be spontaneous [ 2 ]. eIF2 is composed of three subunits, alpha, beta and gamma. The gamma subunit forms the core of the heterotrimer and confers both tRNA binding and GTP/GDP binding [ 3 ].

1. The large subunit of initiation factor aIF2 is a close structural homologue of elongation factors. EMBO J. 21, 1821-32
2. Structural switch of the gamma subunit in an archaeal aIF2 alpha gamma heterodimer. Structure 14, 119-28