The initiation of protein synthesis in eukaryotic cells is regulated by interactions
between protein initiation factors and RNA molecules. The eukaryotic
initiation complex eIF4F exists in vitro as a trimeric complex of eIF4G, eIF4E,
and eIF4A. Together, the complex allows ribosome binding to mRNA by
inducing the unwinding of mRNA secondary structures. eIF4E is a 25 kDa
protein that binds to the mRNA “cap” during an early step in the initiation
of protein synthesis. eIF4A is a 46 kDa protein that acts as an ATP-dependent
RNA helicase. eIF4G is 154 kDa protein that acts as a bridge between eIF4E,
eIF4A, and the eIF3 complex.