Reaction Mechanism
4EGI-1 mimics the action of a class of cellular regulatory molecules that naturally inhibit the binding of two initiation factors necessary for interaction of transcribed mRNA with the subunits of ribosomal complexes. These naturally occurring regulatory molecules, or binding proteins (BPs), as a class known as 4E-BPs, bind to eukaryotic initiation factor (eIF) eIF4E, preventing its association with eIF4G, another initiation factor. These two proteins, under unregulated conditions, form a complex, known as eIF4F, which associates with the 5’ cap of mRNA and the ribosomal subunits. 4E-BPs, as small polypeptides, consist of the same amino acid sequence as the portion of eIF4G that interacts with eIF4E. 4EGI-1 thus prevents the proper association of mRNA, carrying the coded message of transcribed genes, with the ribosome, the cellular component necessary for the translation of those genes into functional proteins. Naturally occurring 4E-BPs are regulated by a protein kinase, mTOR, which through phosphorylation deactivates the binding affinity of 4E-BPs for the eIF4E protein. 1
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