Probable component of the protein complex eIF4F, which is involved in the recognition of the mRNA cap, ATP-dependent unwinding of 5'-terminal secondary structure and recruitment of mRNA to the ribosome. Thought to be a functional homolog of EIF4G1 (By similarity). Interacts with EIF4A, EIF4E, eIF3 and PABPC1. Part of a complex with EIF4E. eIF4F is a multi-subunit complex, the composition of which varies with external and internal environmental conditions. It is composed of at least EIF4A, EIF4E and EIF4G1/EIF4G3. EIF4G1/EIF4G3 interacts through its C-terminus with the serine/threonine kinases MKNK1, and with MKNK2. Appears to act as a scaffold protein, holding these enzymes in place to phosphorylate eIF4E. Non-phosphorylated EIF4EBP1 competes with EIF4G1/EIFG3 to interact with EIF4E; insulin stimulated MAP-kinase (MAPK1 and MAPK3) phosphorylation of EIF4EBP1 causes dissociation of the complex allowing EIF4G1/EIF4G3 to bind and consequent initiation of translation. EIF4G1/EIF4G3 interacts with PABPC1 to bring about circularization of the mRNA (By similarity). Belongs to the eukaryotic initiation factor 4G family. Extended N-terminus. Contaminating sequence. Sequence of unknown origin in the N-terminal part.