Cargo–shell and cargo–cargo couplings govern the mechanics of artificially loaded virus-derived cages

Abstract

Nucleic acids are the natural cargo of viruses and key determinants that affect viral shell stability. In some cases the genome structurally reinforces the shell, whereas in others genome packaging causes internal pressure that can induce destabilization. Although it is possible to pack heterologous cargoes inside virus-derived shells, little is known about the physical determinants of these artificial nanocontainers’ stability. Atomic force and three-dimensional cryo-electron microscopy provided mechanical and structural information about the physical mechanisms of viral cage stabilization beyond the mere presence/absence of cargos. We analyzed the effects of cargo–shell and cargo–cargo interactions on shell stability after encapsulating two types of proteinaceous payloads. While bound cargo to the inner capsid surface mechanically reinforced the capsid in a structural manner, unbound cargo diffusing freely within the shell cavity pressurized the cages up to ~30 atm due to steric effects. Strong cargo–cargo coupling reduces the resilience of these nanocompartments in ~20% when bound to the shell. Understanding the stability of artificially loaded nanocages will help to design more robust and durable molecular nanocontainers.

Exploring the role of genome and structural ions in preventing viral capsid collapse during dehydration

“…Figure 2(A) shows a typical AFM topography of a single TrV particle obtained in the liquid condition. As usual [26,27] the topographical profile, indicated by the blue arrows and depicted in figure 2(G) (blue), indicates that the particle height (~30 nm) is very close to the nominal diameter provided by the crystallographic atomic model (PDB code 3NAP; figure 1(A)). This fact indicates that in our case the virussurface interaction hardly affects the virus' particle structure.…”

Assembly and Mechanical Properties of the Cargo-Free and Cargo-Loaded Bacterial Nanocompartment Encapsulin

“…In-depth structural studies that explore the 19 atomic-scale differences between cargo-loaded and empty encapsulin could shed light on this issue, as it would also allow systematic mechanical testing using the in silico nanoindentation approach described here. Alternatively, the destabilizing effect of cargo binding could follow a similar mechanism as recently proposed for bacteriophage P22 capsids 47 . Here, strong cargocargo coupling decreases the mechanical resilience of the capsid, which could also be the case for hexameric DyP, but is not expected for monomeric TFP.…”

Two-Dimensional Crystallization of P22 Virus-Like Particles

“…Particles without interior cargo seem to be mechanically weaker under the drying and staining conditions, and this is consistent with the mechanical properties of ES in comparison with PC with cargo encapsulated, assessed by AFM (data not shown). 52 The particle−particle distance for ES arrays was found to be 69 nm with diffraction spots extending to the fourth order.…”