This conserved C-terminus appears to be a protein phosphatase-1 catalytic subunit (PP1C) binding region, which may in some circumstances also be retroviral in origin since it is found in both herpes simplex virus and in mouse and man. This domain is found in Gadd-34 apoptosis-associated proteins as well as the constitutive repressor of eIF2-alpha phosphorylation/protein phosphatase 1, regulatory (inhibitor) subunit 15b, otherwise known as CReP. Diverse stressful conditions are associated with phosphorylation of the {alpha} subunit of eukaryotic translation initiation factor 2 (eIF2{alpha}) on serine 51. This signaling event, which is conserved from yeast to mammals, negatively regulates the guanine nucleotide exchange factor, eIF2-B and inhibits the recycling of eIF2 to its active GTP bound form. In mammalian cells eIF2{alpha} phosphorylation emerges as an important event in stress signaling that impacts on gene expression at both the translational and transcriptional levels [1].

1: Inhibition of a constitutive translation initiation factor 2alpha phosphatase, CReP, promotes survival of stressed cells. Jousse C, Oyadomari S, Novoa I, Lu P, Zhang Y, Harding HP, Ron D; J Cell Biol. 2003;163:767-775. PMID:14638860