The translation initiation factor EIF2 catalyzes the first regulated step of protein synthesis initiation, promoting the binding of the initiator tRNA to 40S ribosomal subunits. Binding occurs as a ternary complex of methionyl-tRNA, EIF2, and GTP. EIF2 is composed of 3 nonidentical subunits, the 36-kD EIF2-alpha subunit (EIF2S1), the 38-kD EIF2-beta subunit (EIF2S2, MIM 603908), and the 52-kD EIF2-gamma subunit (EIF2S3, MIM 300161). The rate of formation of the ternary complex is modulated by the phosphorylation state of EIF2-alpha (Ernst et al., 1987 [PubMed 2948954]).[supplied by OMIM, Feb 2010],EIF-2,EIF-2A,EIF-2alpha,EIF2,EIF2A,EIF2S1,Epigenetics & Nuclear Signaling,RNA Binding,Translation Control,Regulation of eIF2,Cell Biology & Developmental Biology,Protein folding,Protein phosphorylation,EIF2S1