(620ad) Dead-Box Helicase and Idp (intrinsically disordered domain) - Molecular Mechanisms By Single Molecule FRET (Rapid Fire)

Intrinsically disordered protein (IDP) motifs have a strong bias in their amino acid sequences, and also they are called as low complexity sequences (LCS). Interestingly, in DDX3 and DDX6 DEAD-box helicase family, ATP driven motor protein, has IDP, and the relationship between IDP and enzymatic function was not understood very well in the past. Here we show that three DEAD-box helicase, DDX3X, LAF1 and GLH-1 from human and C.Elegans has an interesting protein/RNA interaction as RNA enzymes. Those DEAD box helicases share few similarities - possess N-terminal IDP and a helicase core. Our results reveal that 1) they specifically bind single strand (ss) RNA and 2) dynamics of the RNP complex at certain condition. LAF-1 displays no unwinding of double stranded RNA, yet it promotes annealing of complementary ssRNA. ATP enzymatic reaction slows down the dynamics of RNP complex in LAF1. Series of truncation mutants in LAF1 reveal that the N-terminal IDP is responsible for providing the dynamic interaction in that. Together, we unravel the molecular mechanism how IDP motif can be regulated by DEAD-box helicase domain.