title: RNA encapsidation by SV40-derived nanoparticles follows a rapid two-state mechanism.
abstract: Remarkably, uniform virus-like particles self-assemble in a process that appears to follow a rapid kinetic mechanism. The mechanisms by which spherical viruses assemble from hundreds of capsid proteins around nucleic acid, however, are yet unresolved. Using time-resolved small-angle X-ray scattering (TR-SAXS), we have been able to directly visualize SV40 VP1 pentamers encapsidating short RNA molecules (500mers). This assembly process yields T = 1 icosahedral particles comprised of 12 pentamers and one RNA molecule. The reaction is nearly one-third complete within 35 ms, following a two-state kinetic process with no detectable intermediates. Theoretical analysis of kinetics, using a master equation, shows that the assembly process nucleates at the RNA and continues by a cascade of elongation reactions in which one VP1 pentamer is added at a time, with a rate of approximately 10(9) M(-1) s(-1). The reaction is highly robust and faster than the predicted diffusion limit. The emerging molecular mechanism, which appears to be general to viruses that assemble around nucleic acids, implicates long-ranged electrostatic interactions. The model proposes that the growing nucleo-protein complex acts as an electrostatic antenna that attracts other capsid subunits for the encapsidation process.
authors.affiliation: Department of Hematology, Hebrew University-Hadassah Medical School, Jerusalem, Israel 91120.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Kler
authors.forename: Roi
authors.initials: R
authors.lastname: Asor
authors.forename: Chenglei
authors.initials: C
authors.lastname: Li
authors.forename: Avi
authors.initials: A
authors.lastname: Ginsburg
authors.forename: Daniel
authors.initials: D
authors.lastname: Harries
authors.forename: Ariella
authors.initials: A
authors.lastname: Oppenheim
authors.forename: Adam
authors.initials: A
authors.lastname: Zlotnick
authors.forename: Uri
authors.initials: U
authors.lastname: Raviv
mesh_terms: D000818:Animals; D036022:Capsid Proteins / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D053758:Nanoparticles; D009690:Nucleic Acid Conformation; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D053838:Scattering, Small Angle; D013539:Simian virus 40; D055672:Static Electricity; D014961:X-Ray Diffraction
chemical_list: D036022:Capsid Proteins; C062481:VP1 protein, polyomavirus; D012313:RNA