eIF-2B epsilon subunit, central Left-handed parallel beta-Helix (LbH) domain: eIF-2B is a eukaryotic translation initiator, a guanine nucleotide exchange factor (GEF) composed of five different subunits (alpha, beta, gamma, delta and epsilon). eIF2B is important for regenerating GTP-bound eIF2 during the initiation process. This event is obligatory for eIF2 to bind initiator methionyl-tRNA, forming the ternary initiation complex. The eIF-2B epsilon subunit contains an N-terminal domain that resembles a dinucleotide-binding Rossmann fold, a central LbH domain containing 4 turns, each containing three imperfect tandem repeats of a hexapeptide repeat motif (X-[STAV]-X-[LIV]-[GAED]-X), and a C-terminal domain of unknown function that is present in eIF-4 gamma, eIF-5, and eIF-2B epsilon. The epsilon and gamma subunits form the catalytic subcomplex of eIF-2B, which binds eIF2 and catalyzes guanine nucleotide exchange.
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