title: Phosphate release contributes to the rate-limiting step for unwinding by an RNA helicase.
abstract: 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Qixin
authors.initials: Q
authors.lastname: Wang
authors.forename: Jamie J
authors.initials: JJ
authors.lastname: Arnold
authors.forename: Akira
authors.initials: A
authors.lastname: Uchida
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Raney
authors.forename: Craig E
authors.initials: CE
authors.lastname: Cameron
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D055162:Biocatalysis; D007700:Kinetics; D009843:Oligoribonucleotides / Q000737:chemistry / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D011485:Protein Binding; D020365:RNA Helicases / Q000378:metabolism*; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D009843:Oligoribonucleotides; D010710:Phosphates; D020365:RNA Helicases; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases