eIF4B is a multidomain eukaryotic translation initiation factor with a range of activities. It contains one RRM (RNA recognition) domain, a consensus RNA-binding site (RNP-CS) near the N terminus, and a central domain rich in aspartic acid, arginine, tyrosine, and glycine (DRYG). The DRYG domain of eIF4B helps in self-association and interaction with the p170 subunit of eIF3. eIF4B binds to both mRNA and 18S ribosomal RNA and thus acts as a bridge between the mRNA and the 40S ribosomal subunit during translation initiation. The ATPase and RNA helicase activity of the DEAD box protein eIF4A is stimulated by eIF4B and thus functions in close association with eIF4F, a heterotrimeric protein that binds to mRNA cap structure and unwinds inhibitory secondary structure in the 5' untranslated region of eucaryotic mRNAs in an ATP-dependent manner. Ubiquitous expression is seen in most tissues.