The protein eIF-4E is a eukaryotic translation initiation factor. After DNA has been transcribed into mRNA (messenger RNA), some modifications of the newly made mRNA can take place before translation occurs. One such post-transcriptional modification of mRNA is the capping of the 5'-end with 7-methylguanosine (m7-GDP, or m7-Gpp). EIF-4E recognizes and binds to the mRNA cap during the early phases of translation, or protein synthesis. It also helps ribosomal binding by aiding in the unwinding of any mRNA secondary structure. EIF-4E is a subunit of a trimer translation initiation factor eIF-4f, which is also composed of proteins eIF-4G and eIF-4A.
EIF-4E is a conserved protein from the eukaryotic organism Saccharomyces cerevisiae weighing about 25 kDa. It is 213 amino acid residues long and is abundant with secondary structure. It contains 8 beta sheets colored gold, 4 right-handed alpha helices colored blue, and 2 310 alpha helices colored purple.
EIF-4E binds 7-methylguanosine, the post-transcriptional cap of mRNA, as its ligand. Eleven amino acid residues come into contact with this ligand and are as follows: Ala51, Asp53, Trp58, Lys90, Asp92, His94, Glu103, Trp104, Glu105, Ile156, and Arg157.
M7-GDP, or 7N-methyl-8-hydroguanosine-5'-diphosphate, caps cellular eukaryotic mRNAs at their 5'-end after transcription from a DNA template. This post-transcriptional modification has two purposes. First, the cap is essential for ribosomal binding of the mRNAs. Second, it promotes the stability of the mRNAs by preventing their degredation by 5'-exonuleases. The transcription factor eIF-4E recognizes this structure and binds to it.