Promotion of Met-tRNA i Met Binding to Ribosomes by yIF2, a Bacterial IF2 Homolog in Yeast

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Abstract
Delivery of the initiator methionine transfer RNA (Met-tRNAi Met) 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, theSaccharomyces cerevisiae IF2 homolog is shown to function in general translation initiation by promoting Met-tRNAi Met binding to ribosomes. Thus, the mechanism of protein synthesis in eukaryotes and prokaryotes is more similar than was previously realized.