| Type: | Domain | Name: | RNA helicase, DEAD-box type, Q motif |
| Description: | RNA helicases from the DEAD-box family are found in almost all organisms and have important roles in RNA metabolism such as splicing, RNA transport,ribosome biogenesis, translation and RNA decay. They are enzymes that unwind double-stranded RNA molecules in an energy dependent fashion through thehydrolysis of NTP. DEAD-box RNA helicases belong to superfamily 2 (SF2) of helicases. As other SF1 and SF2 members they contain seven conserved motifswhich are characteristic of these two superfamilies [].DEAD-box is named after the amino acids of motif II or Walker B (Mg2+-binding aspartic acid). Besides these seven motifs, DEAD-box RNA helicases contain aconserved cluster of nine amino-acids (the Q motif) with an invariant glutamine located N-terminally of motif I. An additional highly conserved butisolated aromatic residue is also found upstream of these nine residues [].The Q motif is characteristic of and unique to DEAD box family of helicases.It is supposed to control ATP binding and hydrolysis, and therefore it represents a potential mechanism for regulating helicase activity.Several structural analyses of DEAD-box RNA helicases have been reported [, ]. The Q motif is located in close proximity to motif I. Theconserved glutamine and aromatic residues interact with the ADP molecule.Some proteins known to contain a Q motif: Eukaryotic initiation factor 4A (eIF4A). An ATP-dependent RNA helicase which is a subunit of the eIF4F complex involved in cap recognition andrequired for mRNA binding to ribosome.Various eukaryotic helicases involved in ribosome biogenesis (DBP3, DRS1, SPB4, MAK5, DBP6, DBP7, DBP9, DBP10).Eukaryotic DEAD-box proteins involved in pre-mRNA splicing (Prp5p, Prp28p and Sub2p).DEAD-box proteins required for mitochondrial genome expression (MSS116 and MRH4).Fungi ATP-dependent RNA helicase DHH1. It is required for decapping and turnover of mRNA.Fungi ATP-dependent RNA helicase DBP5. It is involved in nucleo-cytoplasmic transport of poly(A) RNA.Bacterial ATP-dependent RNA helicase rhlB. It is involved in the RNA degradosome, a multi-enzyme complex important in RNA processing andmessenger RNA degradation.Bacterial cold-shock DEAD box protein A.This entry represents a region stretching from the conserved aromatic residue to one amino acid after the glutamine of the Q motif. | Short Name: | RNA_helicase_DEAD_Q_motif |
