Promotion of met-tRNAiMet binding to ribosomes by yIF2, a bacterial IF2 homolog in yeast.

Delivery of the initiator methionine transfer RNA (Met-tRNAiMet) to the ribosome is a key step in the initiation of protein synthesis. Previous results have indicated that this step is catalyzed by the structurally dissimilar translation factors in prokaryotes and eukaryotes-initiation factor 2 (IF2) and eukaryotic initiation factor 2 (eIF2), respectively. A bacterial IF2 homolog has been identified in both eukaryotes and archaea. By using a combination of molecular genetic and biochemical studies, the Saccharomyces cerevisiae IF2 homolog is shown to function in general translation initiation by promoting Met-tRNAiMet binding to ribosomes. Thus, the mechanism of protein synthesis in eukaryotes and prokaryotes is more similar than was previously realized.