title: Forces from the Portal Govern the Late-Stage DNA Transport in a Viral DNA Packaging Nanomotor.
abstract: In the Phi29 bacteriophage, the DNA packaging nanomotor packs its double-stranded DNA genome into the virus capsid. At the late stage of DNA packaging, the negatively charged genome is increasingly compacted at a higher density in the capsid with a higher internal pressure. During the process, two Donnan effects, osmotic pressure and Donnan equilibrium potentials, are significantly amplified, which, in turn, affect the channel activity of the portal protein, GP10, embedded in the semipermeable capsid shell. In the research, planar lipid bilayer experiments were used to study the channel activities of the viral protein. The Donnan effect on the conformational changes of the viral protein was discovered, indicating GP10 may not be a static channel at the late stage of DNA packaging. Due to the conformational changes, GP10 may generate electrostatic forces that govern the DNA transport. For the section of the genome DNA that remains outside of the connector channel, a strong repulsive force from the viral protein would be generated against the DNA entry; however, for the section of the genome DNA within the channel, the portal protein would become a Brownian motor, which adopts the flash Brownian ratchet mechanism to pump the DNA against the increasingly built-up internal pressure (up to 20 atm) in the capsid. Therefore, the DNA transport in the nanoscale viral channel at the late stage of DNA packaging could be a consequence of Brownian movement of the genomic DNA, which would be rectified and harnessed by the forces from the interior wall of the viral channel under the influence of the Donnan effect.
authors.affiliation: Department of Chemistry, College of Arts and Sciences, Indiana University-Purdue University Fort Wayne, Fort Wayne, Indiana. Electronic address: jingp@ipfw.edu.
authors.forename: Peng
authors.initials: P
authors.lastname: Jing
authors.affiliation: Department of Chemistry, College of Arts and Sciences, Indiana University-Purdue University Fort Wayne, Fort Wayne, Indiana.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Burris
authors.affiliation: Division of Endocrinology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
mesh_terms: D017103:Bacillus Phages / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D001696:Biomechanical Phenomena; D036022:Capsid Proteins / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D042003:DNA Packaging; D004279:DNA, Viral / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism; D055595:Mechanical Phenomena; D049329:Nanostructures; D009995:Osmosis; D055672:Static Electricity; D013269:Stochastic Processes
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; D008051:Lipid Bilayers; C097975:portal protein, bacteriophage phi29