title: Functional visualization of viral molecular motor by hydrogen-deuterium exchange reveals transient states.
abstract: Molecular motors undergo cyclical conformational changes and convert chemical energy into mechanical work. The conformational dynamics of a viral packaging motor, the hexameric helicase P4 of dsRNA bacteriophage phi8, was visualized by hydrogen-deuterium exchange and high-resolution mass spectrometry. Concerted changes of exchange kinetics revealed a cooperative unit that dynamically links ATP-binding sites and the central RNA-binding channel. The cooperative unit is compatible with a structure-based model in which translocation is mediated by a swiveling helix. Deuterium labeling also revealed the transition state associated with RNA loading, which proceeds via opening of the hexameric ring. The loading mechanism is similar to that of other hexameric helicases. Hydrogen-deuterium exchange provides an important link between time-resolved spectroscopic observations and high-resolution structural snapshots of molecular machines.
authors.affiliation: Institute of Biotechnology and Department of Biological and Environmental Sciences, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Jirí
authors.initials: J
authors.lastname: Lísal
authors.forename: Tukiet T
authors.initials: TT
authors.lastname: Lam
authors.forename: Denis E
authors.initials: DE
authors.lastname: Kainov
authors.forename: Mark R
authors.initials: MR
authors.lastname: Emmett
authors.forename: Alan G
authors.initials: AG
authors.lastname: Marshall
authors.forename: Roman
authors.initials: R
authors.lastname: Tuma
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D001665:Binding Sites; D041961:Deuterium Exchange Measurement; D007700:Kinetics; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D019906:Nuclear Magnetic Resonance, Biomolecular; D020836:Protein Structure, Quaternary / Q000187:drug effects; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D020409:Molecular Motor Proteins; D014764:Viral Proteins; D012313:RNA; D000255:Adenosine Triphosphate