Local stabilization of subunit-subunit contacts causes global destabilization of Hepatitis B virus capsids

Abstract

<jats:title>Abstract</jats:title><jats:p>Development of antiviral molecules that bind virion is a strategy that remains in its infancy and the details of their mechanisms are poorly understood. Here we investigate the behavior of DBT1, a dibenzothiazapine, which specifically interacts with the capsid protein of Hepatitis B Virus (HBV). We found that DBT1 stabilizes protein-protein interaction, accelerates capsid assembly, and can induce formation of aberrant particles. Paradoxically, DBT1 can cause pre-formed capsids to dissociate. These activities may lead to (i) assembly of empty and defective capsids, inhibiting formation of new virus and (ii) disruption of mature viruses, which are metastable, to inhibit new infection. Using cryo-electron microscopy we observed that DBT1 led to asymmetric capsids where well-defined DBT1 density was bound at all inter-subunit contacts. These results suggest that DBT1 can support assembly by increasing buried surface area but induce disassembly of metastable capsids by favoring asymmetry to induce structural defects.</jats:p>

Core Protein-Directed Antivirals and Importin β Can Synergistically Disrupt HBV Capsids

“…In sub-saturating conditions, when HAP fills B and C sites, capsids are stabilized (13). We observe that when there is enough HAP to fill all four classes of site, capsids are destabilized because HAPs disrupt icosahedral geometry (14, 40). We showed that untreated or sub-saturating HAP12 conditions did not increase CTD sensitivity to protease activity in empty capsids.…”

“…These small molecules increase the association energy of interdimer contacts (13, 15). However, by locally distorting the interdimer interface, HAPs can disturb global icosahedral geometry (15–17, 40, 45, 46). As more HAPs bind, a global cascading effect on capsid structure leads to deformation and eventually disruption (14–17, 40).…”

“…However, by locally distorting the interdimer interface, HAPs can disturb global icosahedral geometry (15–17, 40, 45, 46). As more HAPs bind, a global cascading effect on capsid structure leads to deformation and eventually disruption (14–17, 40). HAP12 concentration also differentially affects CTD and capsid dynamics.…”

“…In a T=4 capsid, there are A, B, C, and D pockets, each capped by a neighboring subunit. HAPs preferentially bind B and C sites; A and D sites are sterically hindered (see Figure 3a in reference (40)). In sub-saturating conditions, when HAP fills B and C sites, capsids are stabilized (13).…”

Molecular Mechanism of Capsid Disassembly in Hepatitis B Virus

“…These variations result from asymmetric capsid motions and distortions due to stochastic thermal fluctuations, which are also reported in previous studies of viral capsids and speculated to be of biological importance for disassembly. 22,30,31 The variability in the average root mean square deviations (RMSDs) of the proteins within the capsid also points to their inherent structural heterogeneity due to thermal fluctuations ( Fig. S3).…”