The eIF4F complex is composed of three subunits: eIF4A, eIF4E, and eIF4G. Each subunit has multiple human isoforms and there exist additional eIF4 proteins: eIF4B and eIF4H.
eIF4G is a 175.5-kDa scaffolding protein that interacts with eIF3 and the Poly(A)-binding protein (PABP), as well as the other members of the eIF4F complex. eIF4E recognizes and binds to the 5' cap structure of mRNA, while eIF4G binds PABP, which binds the poly(A) tail, potentially circularizing and activating the bound mRNA. eIF4Aa DEAD box RNA helicaseis important for resolving mRNA secondary structures.
eIF4B contains two RNA-binding domainsone non-specifically interacts with mRNA, whereas the second specifically binds the 18S portion of the small ribosomal subunit. It acts as an anchor, as well as a critical co-factor for eIF4A.  It is also a substrate of S6K, and when phosphorylated, it promotes the formation of the pre-initiation complex.  In vertebrates, eIF4H is an additional initiation factor with similar function to eIF4B.