mRNA-induced dissociation of initiation factor 2

The GTP-dependent initiator methionyl-tRNA (Met-tRNAi) binding protein, eukaryotic initiation factor 2 (eIF2), binds mRNA, as well as Met-tRNAi with high affinity and both RNA species appear to bind to the 48,000-dalton subunit of eIF2. Binding of mRNA by eIF2 produces an alteration in its molecular configuration resulting in dissociation of component subunits as assayed by isoelectric focusing. In contrast, GTP, GDP, or Met-tRNAi produce no subunit dissociation. Phosphorylation of the 37,000-dalton eIF2 subunit by the heme-controlled translational repressor does not alter the ability of mRNA to produce subunit dissociation of eIF2. A role for mRNA binding by eIF2 in initiation of protein synthesis or in recycling of eIF2, or both, is postulated.