Eukaryotic initiation factor 2B (eIF2B).

Eukaryotic initiation factor 2B (eIF2B) is a guanine nucleotide-exchange factor which mediates the exchange of GDP (bound to initiation factor eIF2) for GTP, thus regenerating the active [eIF2.GTP] complex that is required for peptide-chain initiation. The activity of eIF2B is a key control point for eukaryotic protein synthesis and is altered in response to viral infection, hormones, nutrients, growth factors and certain stresses. It may be regulated directly by its own phosphorylation, phosphorylation of its substrate, eIF2 and by allosteric effectors. Understanding its regulation will lead to a better knowledge of insulin action, regulation of the immune system and of insulin production in the pancreas.