Mechanical Disassembly of Single Virus Particles Reveals Kinetic Intermediates Predicted by Theory

Abstract

New experimental approaches are required to detect the elusive transient intermediates predicted by simulations of virus assembly or disassembly. Here, an atomic force microscope (AFM) was used to mechanically induce partial disassembly of single icosahedral T=1 capsids and virions of the minute virus of mice. The kinetic intermediates formed were imaged by AFM. The results revealed that induced disassembly of single minute-virus-of-mice particles is frequently initiated by loss of one of the 20 equivalent capsomers (trimers of capsid protein subunits) leading to a stable, nearly complete particle that does not readily lose further capsomers. With lower frequency, a fairly stable, three-fourths-complete capsid lacking one pentamer of capsomers and a free, stable pentamer were obtained. The intermediates most frequently identified (capsids missing one capsomer, capsids missing one pentamer of capsomers, and free pentamers of capsomers) had been predicted in theoretical studies of reversible capsid assembly based on thermodynamic-kinetic models, molecular dynamics, or oligomerization energies. We conclude that mechanical manipulation and imaging of simple virus particles by AFM can be used to experimentally identify kinetic intermediates predicted by simulations of assembly or disassembly.

Calcium Ions Modulate the Mechanics of Tomato Bushy Stunt Virus

“…Previous mechanical studies of VNPs have shown that the AFM tip usually removes individual structural components (16,19,26,36) after the elastic limit. In contrast, our data show that FICs induce an irreversible deformation of the structure without showing capsomeric vacancies.…”

“…FIC 1 responds linearly until it reaches a force of~4.8 nN, where a sharp drop of the force is registered (elastic limit). The elastic limit is ascribed to the breakage of the particle, which implies the shell cracking (35) or the loss of various capsomers (26,36). However, in this case, immediate imaging of the particle demonstrates the absence of capsomeric vacancies and a height decrease of <2 nm (Fig.…”

Stalking Higher Energy Conformers on the Potential Energy Surface of Charged Species

“…10 The mechanical manipulation and imaging of virus particles by Atomic Force Microscopy was used to identify kinetic intermediates predicted by simulations of assembly and/or disassembly. 11 Of direct relevance to the present work, a number of gas-phase investigations are bearing on the dynamics of conformational isomerization and kinetic trapping. Conformational distributions of bradykinin have been studied by Rizzo and co-workers, 12 showing the appearance of high energy conformers.…”

Microscopie à force atomique pour l’étude du cycle viral

“…Comme en cryo-EM, la résolution de cette méthode est telle qu'il est possible d'observer les protubérances des protéines de structure de certains virus non enveloppés qui sont en général à symétrie icosaédrique, et d'en déterminer leur nombre de triangulation ainsi que leurs axes de symétrie [30]. En couplant la haute résolution pour l'imagerie et les expériences de nano-indentation, l'AFM permet de déterminer des effets subtils comme le rôle mécanique du génome présent au sein de la capside.…”