Solution Structure of Human Initiation Factor eIF2α Reveals Homology to the Elongation Factor eEF1B

AbstractThe GTP-bound form of the trimeric eukaryotic translation initiation factor 2 (eIF2) transfers aminoacylated initiator methionyl tRNA onto the 40S ribosome. We have solved with solution NMR the structure of the α subunit of human eIF2 (heIF2α). The protein consists of two domains that are mobile relative to each other. The N-terminal domain has an S1-type oligonucleotide/oligosaccharide binding-fold subdomain and an α-helical subdomain. The C-terminal domain adopts an αβ-fold very similar to the C-terminal domain of elongation factor (eEF) 1Bα, the guanine-nucleotide exchange factor for eEF1A. The structural and functional similarities found between eIF2α/eIF2γ and eEF1Bα/eEF1A suggest a model for the interaction of eIF2α with eIF2γ, and eIF2 with Met-tRNAiMet. It further indicates a previously unrecognized evolutionary lineage of eIF2α/γ from the functionally related elongation factor eEF1Bα/eEF1A complex