Domain structure of DDX3. Two tandem RecA-like domains (red) are flanked by the low complexity domains at the N and C terminals (gray). Twelve signature motifs shared by DEAD-box family proteins are shown inside the RecA-like domains. The motif II contains the motif DEAD that defines the family. Two nuclear export signals (NESs) and an eIF4E-binding region are also shown. The newly defined functional core (Ref 26) not only contains the central RecA-like domains but also includes abutting NTE and CTE. See the text for detailed description. Numbers indicate positions of amino acid residues from the N to the C terminus.