eIF2 is a heterotrimer of a total molar mass of 126 kDa that is composed of the three sub-units: α (sub-unit 1), β (sub-unit 2), and γ (sub-unit 3). 
The sequences of all three sub-units are highly conserved (pairwise amino acid identities for each sub-unit range from 47 to 72% when comparing the proteins of Homo sapiens and Saccharomyces cerevisiae).
The α-subunit contains the main target for phosphorylation, a serine at position 51. It also contains a S1 motif domain, which is a potential RNA binding-site. Therefore, the α-subunit can be considered the regulatory subunit of the trimer.
The β-subunit contains multiple phosphorylation sites (residues 2, 13, 67, 218). What is important to consider is that there are also three lysine clusters in the N-terminal domain (NTD), which are important for the interaction with eIF2B. Moreover, the sequence of the protein comprises a zinc finger motif that was shown to play a role in both ternary complex and 43S preinitiation complex formation. There are also two guanine nucleotide-binding sequences that have not been shown to be involved in the regulation of eIF2 activity. The β-subunit is also believed to interact with both tRNA and mRNA.
The γ-subunit comprises three guanine nucleotide-binding sites and is known to be the main docking site for GTP/GDP. It also contains a tRNA-binding cavity that has been shown by X-ray crystallography. A zinc knuckle motif is able to bind one Zn cation. It is related to some elongation factors like EF-Tu.