No Hydrolysis Needed

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Science  16 Jan 2009:
Vol. 323, Issue 5912, pp. 310
DOI: 10.1126/science.323.5912.310b

DEAD-box proteins facilitate RNA rearrangements that locally disrupt secondary or tertiary structure or RNA/protein interactions. They are structurally similar to DNA helicases that use the energy from ATP hydrolysis to unwind double-stranded DNA, but they do not appear to move very far along the RNA, although they can pry apart short duplex regions. Two groups show that RNA strand separation depends directly on ATP binding rather than hydrolysis. Chen et al. report that the DEAD-box proteins CYT-19, Mss116p, and Ded1p achieve complete separation of short RNA duplexes with the hydrolysis of one or, under some conditions, even less than one ATP. Strand separation depends on ATP binding, which probably stabilizes a protein conformation that favors strand separation. Consistent findings are obtained by Liu et al., who report that Ded1p, Mss116p, and eIF4A can separate short duplexes upon binding the ATP analog ADP-BeFx, which is a mimic of the prehydrolysis state of ATP. They go on to show that ATP hydrolysis promotes dissociation of the protein from the RNA and thus is required for efficient enzyme recycling. Intriguingly, even though ATP hydrolysis does not fuel translocation in these DEAD-box proteins, the related DExD/H helicase RIG-1, which detects viral RNA and elicits an antiviral signaling cascade, undergoes ATP-dependent translocation on double-stranded RNA without unwinding it (see Myong et al., Reports, Science Express, 1 January 2009). — VV

Proc. Natl. Acad. Sci. U.S.A. 105, 20203; 20209 (2008).

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