Multiscale modelization in a small virus: Mechanism of proton channeling and its role in triggering capsid disassembly

by Juan Francisco Viso, Patricia Belelli, Mat ías Machado, Humberto González, Sergio Pantano, María Julia Amundarain, Fernando Zamarreño, Maria Marta Branda, Diego M. A. Guérin, Marcelo D. Costabel In this work, we assess a previously advanced hypothesis that predicts the existence of ion channels in the capsid of small and non-enveloped icosahedral viruses. With this purpose we examineTriatoma Virus (TrV) as a case study. This virus has a stable capsid under highly acidic conditions but disassembles and releases the genome in alkaline environments. Our calculations range from a subtle sub-atomic proton interchange to the dismantling of a large-scale system representing several million of atoms. Our results provide structure-based explanations for the three roles played by the capsid to enable genome release. First, we observe, for the first time, the formation of a hydrophobic gate in the cavity along the five-fold axis of the wild-type virus capsid, which can be disrupted by an ion located in the pore. Second, the channel enables protons to permeate the capsid through a unidirectional Grotthuss-like mechanism, which is the most likely process through which the capsid senses pH. Finally, assuming that the proton leak promotes a charge imbalance in the interior of the capsid, we model an internal pressure that forces shell cracking using coarse-grained simulations. Although qualitatively, this last step could represent the mechanism of capsid opening that allows RNA rel...
Source: PLoS Computational Biology - Category: Biology Authors: Source Type: research