What is a DEAD-box RNA helicase?
Helicase proteins are classically defined as ATP-dependent enzymes that separate DNA and/or RNA duplexes, and they are divided into superfamilies (SFs) I–III based on sequence similarity, without distinguishing between DNA and RNA helicases (5). Many RNA helicases have been shown to have ATPase activity in the presence of RNA, but not all have demonstrated actual unwinding activity, probably due to a lack of specific substrates and/or cofactors in an in vitro system (6). RNA helicases may also exhibit other activities, such as disrupting RNA-protein complexes (6). Thus, RNA helicase function is presently not fully defined. Members of the helicase families share several conserved motifs, including the Walker A and B motifs, which are involved in the binding of nucleoside triphosphates. The DExD/H-box RNA helicases (named for the consensus amino acid sequence of the Walker B motif) belong to the second superfamily of helicases (SF-II) and are divided into 3 families: Ski 2, DEAH-box, and
