Translation initiation factor eIF2B subunit epsilon

UniProtKB accession:  P32501

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UniProtKB description:  Acts as a catalytic component of the translation initiation factor 2B (eIF2B) complex, which catalyzes the exchange of GDP for GTP on eukaryotic initiation factor 2 (eIF2) and is regulated by phosphorylated eIF2. Its guanine nucleotide exchange factor activity is repressed when bound to eIF2 complex phosphorylated on the alpha subunit, thereby limiting the amount of methionyl-initiator methionine tRNA available to the ribosome and consequently global translation is repressed (By similarity). It activates the synthesis of GCN4 in yeast under amino acid starvation conditions by suppressing the inhibitory effects of multiple AUG codons present in the leader of GCN4 mRNA. It may promote either repression or activation of GCN4 expression depending on amino acid availability. GCD6 and GCD7 repress GCN4 expression at the translational level by ensuring that ribosomes which have translated UORF1 will reinitiate at UORF2, -3, or -4 and thus fail to reach the GCN4 start site.