Catalyzes the exchange of eukaryotic initiation factor 2-bound GDP for GTP. Complex of five different subunits; alpha, beta, gamma, delta and epsilon. Interacts with RGS2 (By similarity). Phosphorylated at Ser-540 by DYRK2; this is required for subsequent phosphorylation by GSK3B. Phosphorylated on serine and threonine residues by GSK3B; phosphorylation inhibits its function (By similarity). Polyubiquitinated, probably by NEDD4. Belongs to the eIF-2B gamma/epsilon subunits family.