RNA Encapsidation by SV40-Derived Nanoparticles Follows a Rapid Two-State Mechanism

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• 作者：Stanislav Kler ; Roi Asor ; Chenglei Li ; Avi Ginsburg ; Daniel Harries ; Ariella Oppenheim ; Adam Zlotnick ; Uri Raviv
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：May 30, 2012
• 年：2012
• 卷：134
• 期：21
• 页码：8823-8830
• 全文大小：395K
• 年卷期：v.134,no.21(May 30, 2012)
• ISSN：1520-5126

文摘

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 10⁹ M^鈥? s^鈥?. 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.