Initiation of protein synthesis in eukaryotes. Nature of ternary complex dissociation factor.

Excessive concentrations of the eukaryotic initiation factor 2(eIF-2).stimulating protein, a factor that catalyzes the formation of binary (GTP.eIF-2) and ternary (GTP.eIF-2.initiator methionyl-tRNA) initiation complexes at physiological Mg2+ concentrations, can cause ternary complex dissociation when the Mg2+ concentration is raised from 0.5 to 5.0 mM. Stimulation of ternary complex formation and dissociation have similar (a) pH optima, (b) metal ion specificity, and (c) sensitivity to phosphorylation of the eIF-2 alpha subunit. The results suggest that ternary complex dissociation is an artifact with no physiological significance.