eIF2 is the main protein complex responsible for delivering the initiator tRNA to the P-site of the preinitiation complex, as a ternary complex containing Met-tRNA and GTP (the eIF2-TC).  eIF2 has specificity for the methionine-charged initiator tRNA, which is distinct from other methionine-charged tRNAs used for elongation of the polypeptide chain. The eIF2 ternary complex remains bound to the P-site while the mRNA attaches to the 40s ribosome and the complex begins to scan the mRNA. Once the  AUG start codon is recognized and located in the P-site, eIF5 stimulates the hydrolysis of eIF2-GTP, effectively switching it to the GDP-bound form via gated phosphate release. The hydrolysis of eIF2-GTP provides the conformational change to change the scanning complex into the 48S Initiation complex with the initiator tRNA-Met anticodon base paired to the AUG. After the initiation complex is formed the 60s subunit joins and eIF2 along with most of the initiation factors dissociate from the complex allowing the 60S subunit to bind. eIF1A and eIF5B-GTP remain bound to one another in the A site and must be hydrolyzed to be released and properly initiate elongation.
eIF2 has three subunits, eIF2-α, β, and γ. The former α-subunit is a target of regulatory phosphorylation and is of particular importance for cells that may need to turn off protein synthesis globally as a response to cell signaling events. When phosphorylated, it sequesters eIF2B (not to be confused with eIF2β), a GEF. Without this GEF, GDP cannot be exchanged for GTP, and translation is repressed. One example of this is the eIF2α-induced translation repression that occurs in reticulocytes when starved for iron. In the case of viral infection, protein kinase R (PKR) phosphorylates eIF2α when dsRNA is detected in many multicellular organisms, leading to cell death.
The proteins eIF2A and eIF2D are both technically named eIF2 but neither are part of the eIF2 heterotrimer and they seem to play unique functions in translation. Instead, they appear to be involved in specialized pathways, such as eIF2-independent translation initiation or re-initiation, respectively.