title: Affinity of molecular interactions in the bacteriophage phi29 DNA packaging motor.
abstract: DNA packaging in the bacteriophage phi29 involves a molecular motor with protein and RNA components, including interactions between the viral connector protein and molecules of pRNA, both of which form multimeric complexes. Data are presented to demonstrate the higher order assembly of pRNA together with the affinity of pRNA:pRNA and pRNA:connector interactions, which are used to propose a model for motor function. In solution, pRNA can form dimeric and trimeric multimers in a magnesium-dependent manner, with dissociation constants for multimerization in the micromolar range. pRNA:connector binding is also facilitated by the presence of magnesium ions, with a nanomolar apparent dissociation constant for the interaction. From studies with a mutant pRNA, it appears that multimerization of pRNA is not essential for connector binding and it is likely that connector protein is involved in the stabilization of higher order RNA multimers. It is proposed that magnesium ions may promote conformational change that facilitate pRNA:connector interactions, essential for motor function.
authors.affiliation: Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Robinson
authors.forename: Jonathan P A
authors.initials: JP
authors.lastname: Wood
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Capaldi
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Baron
authors.forename: Christopher
authors.initials: C
authors.lastname: Gell
authors.forename: D Alastair
authors.initials: DA
authors.lastname: Smith
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Stonehouse
mesh_terms: D017103:Bacillus Phages / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D036022:Capsid Proteins / Q000378:metabolism*; D004279:DNA, Viral / Q000737:chemistry; D008969:Molecular Sequence Data; D012367:RNA, Viral / Q000737:chemistry* / Q000378:metabolism*; D019065:Virus Assembly
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; D012367:RNA, Viral; C097975:portal protein, bacteriophage phi29