DDX19B is an ATP-dependent RNA helicase involved in the export of mRNA from the nucleus. According to UniProt, it does not function primarily by unwinding RNA duplexes. Instead it acts as a remodeler of ribonucleoprotein particles: proteins bound to nuclear mRNA are dissociated and replaced by cytoplasmic mRNA-binding proteins. NCBI Gene reports that the protein shows RNA-dependent ATPase and ATP-dependent RNA-unwinding activities, and that it is recruited to the cytoplasmic fibrils of the nuclear pore complex, where it takes part in mRNA export.

The DDX19B gene encodes a member of the DEAD-box helicase family, assigned to the DDX19/DBP5 subfamily. DEAD-box proteins are defined by the conserved Asp-Glu-Ala-Asp (DEAD) motif and are putative RNA helicases. As a family, they are implicated in processes that alter RNA secondary structure, including translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly. Some members are thought to contribute to embryogenesis, spermatogenesis, and cellular growth and division. DDX19B is found in the cytoplasm and in the nucleoplasm, and multiple alternatively spliced transcript variants encoding different isoforms have been described.

The name DBP5 reflects the yeast homologue, Dbp5, and earlier HGNC names described the gene as DEAD/H box polypeptide 19 (Dbp5, yeast, homolog) and DEAD box polypeptide 19B. These names remain in use in the literature, so searches for DDX19B, DDX19 and DBP5 often refer to the same target. Researchers study the protein to understand how mRNA export is coupled to remodelling of messenger ribonucleoprotein complexes at the nuclear pore.