Eukaryotic Translation Initiation Factor 5B (EIF5B)

Translation initiation requires the delivery of the initiator methionine tRNA to the 40S ribosomal subunit. The initiator methionine tRNA is delivered by the heterotrimeric complex EIF2 in a ternary complex with GTP that interacts with the 40S subunit. The resulting complex then binds to an mRNA and scans for the AUG start codon.Sequence analysis predicted that the 1,220-amino acid human IF2 protein, which is 44% identical to the yeast protein, contains 3 motifs characteristic of GTP-binding proteins and has long N-terminal poly-glu and poly-lys stretches. The GTP-binding domains of human IF2 share 70% and 54% identity with those of the yeast and archaeal IF2 proteins, respectively. Northern blot analysis revealed wide expression of a 4.5-kb IF2 transcript, with highest levels in testis and skeletal muscle.