Roles of Eukaryotic Initiation Factor 2 and Eukaryotic Initiation Factor 2 Ancillary Protein Factors in Eukaryotic Protein Synthesis Initiation

The available evidence indicates that although the basic steps of peptide chain initiation are similar in all eukaryotic cells, the specific regulatory mechanisms may be different in animal cells and in lower eukaryotic cells. The basic steps are: (1) formation of a ternary complex between eukaryotic peptide chain initiation factor 2 (eIF-2), Met-transfer RNA (tRNA)f, and GTP: Met-tRNAf · elF-2 · GTP; (2) transfer of Met-tRNAf to 40 S ribosomes and formation of the Met-tRNAf · 40 S · messenger RNA (mRNA) complex; and (3) joining of the Met-tRNAf · 40 S · mRNA complex with 60 S ribosomes and the formation of the Met-tRNAf · 80 S · mRNA complex.