title: Electrostatic properties of cowpea chlorotic mottle virus and cucumber mosaic virus capsids.
abstract: Electrostatic properties of cowpea chlorotic mottle virus (CCMV) and cucumber mosaic virus (CMV) were investigated using numerical solutions to the Poisson-Boltzmann equation. Experimentally, it has been shown that CCMV particles swell in the absence of divalent cations when the pH is raised from 5 to 7. CMV, although structurally homologous, does not undergo this transition. An analysis of the calculated electrostatic potential confirms that a strong electrostatic repulsion at the calcium-binding sites in the CCMV capsid is most likely the driving force for the capsid swelling process during the release of calcium. The binding interaction between the encapsulated genome material (RNA) inside of the capsid and the inner capsid shell is weakened during the swelling transition. This probably aids in the RNA release process, but it is unlikely that the RNA is released through capsid openings due to unfavorable electrostatic interaction between the RNA and capsid inner shell residues at these openings. Calculations of the calcium binding energies show that Ca(2+) can bind both to the native and swollen forms of the CCMV virion. Favorable binding to the swollen form suggests that Ca(2+) ions can induce the capsid contraction and stabilize the native form.
authors.affiliation: Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, 92093-0365, USA. rok@ucsd.edu
authors.forename: Robert
authors.initials: R
authors.lastname: Konecny
authors.forename: Joanna
authors.initials: J
authors.lastname: Trylska
authors.forename: Florence
authors.initials: F
authors.lastname: Tama
authors.forename: Deqiang
authors.initials: D
authors.lastname: Zhang
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Baker
authors.forename: Charles L
authors.initials: CL
authors.lastname: Brooks
authors.forename: J A
authors.initials: JA
authors.lastname: McCammon
mesh_terms: D001665:Binding Sites; D017795:Bromovirus / Q000737:chemistry*; D002118:Calcium / Q000378:metabolism; D002213:Capsid / Q000737:chemistry*; D036022:Capsid Proteins / Q000737:chemistry; D003198:Computer Simulation; D017799:Cucumovirus / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D008958:Models, Molecular; D012367:RNA, Viral / Q000378:metabolism; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D036022:Capsid Proteins; D008024:Ligands; D012367:RNA, Viral; D002118:Calcium