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Nucleic Acids Res. 2010 Mar;38(4):1312-24. doi: 10.1093/nar/gkp1118. Epub 2009 Dec 6.

Phosphate release contributes to the rate-limiting step for unwinding by an RNA helicase.

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  • 1Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.


RNA helicases function in numerous aspects of RNA biology. These enzymes are RNA-stimulated ATPases that translocate on RNA and unwind or remodel structured RNA in an ATP-dependent fashion. How ATP and the ATPase cycle fuel the work performed by helicases is not completely clear. The hepatitis C virus RNA helicase, NS3, is an important model system for this class of enzymes. NS3 binding to a single-/double-strand RNA or DNA junction leads to ATP-independent melting of the duplex and formation of a complex capable of ATP-dependent unwinding by using a spring-loaded mechanism. We have established an RNA substrate for NS3 that can be unwound in a single sub-step. Our studies are consistent with a model in which a single ATP binding and/or hydrolysis event sets the unwinding spring and phosphate dissociation contributes to release of the spring, thereby driving the power stroke used for unwinding.

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