Affinity of molecular interactions in the bacteriophage phi29 DNA packaging motor.
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.
Robinson
Mark A
MA
Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
Wood
Jonathan P A
JP
Capaldi
Stephanie A
SA
Baron
Andrew J
AJ
Gell
Christopher
C
Smith
D Alastair
DA
Stonehouse
Nicola J
NJ
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
D036022:Capsid Proteins; D004279:DNA, Viral; D012367:RNA, Viral; C097975:portal protein, bacteriophage phi29