EIF-5A, also known as EIF5, functions in start site selection as a GTPase accelerating protein (GAP) for the eukaryotic translation initiation factor (eIF) 2•GTP•tRNA ternary complex within the ribosome-bound pre-initiation complex. In protein synthesis initiation, eIF2 functions in its GTP-bound state to deliver initiator methionyl-tRNA to the small ribosomal subunit and is necessary for protein synthesis in all cells. EIF-5A stabilizes the binding of GDP to eIF2 and is therefore a bi-functional protein that acts as a GDP dissociation inhibitor (GDI). EIF-5A also interacts with eIF1 and eIF3 and binds the eIF2-GTP/Met-tRNA ternary complex along with the 40S ribosome subunit.
