Poster abstracts
Poster number 9 submitted by Margaret Bohmer
Construction of a hexameric pRNA ring with 12 motifs to interact with the dodecameric channel of the phi29 ATPase motor for dsDNA packaging and virion production
Margaret Bohmer, Peixuan Guo
Abstract:
DsDNA translocation is ubiquitous in living systems, including DNA replication, binary fission, and homologous recombination. A common mechanism to avoid the coiling and tangling in translocating the lengthy genome involves an asymmetrical hexameric ATPase motor with a sequential revolving mechanism. One motor that uses this mechanism is the phi29 DNA-packaging motor, which uses an RNA ring (pRNA) to gear the motion for dsDNA translocation. The stoichiometry of this pRNA ring (pentamer or hexamer) has been debated for decades. One argument against the hexameric RNA model is that if six copies of pRNA cannot form a stable structure with the 12-subunit connector, and therefore the pRNA must be a pentamer that binds the pentameric capsid vertex. In this study, we constructed a pRNA chimera that composed of the phi29 motor pRNA and the M2 phage motor pRNA to determine the stoichiometry of the motor pRNA ring. Biochemical and computational approaches revealed that the newly constructed biologically active pRNA hexameric ring contains 12 motifs that can bind to the dodecameric ATPase motor channel, with each pRNA having two points of contact with the motor. The newly constructed pRNA hexamer was biologically active in dsDNA packaging, leading to the production of infectious virion. Our experiments with mutant pRNA demonstrate the stoichiometry of the pRNA ring is a common multiple of two and three, which is six.
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