Norovirus Capsid Proteins Self-Assemble through Biphasic Kinetics via Long-Lived Stave-like Intermediates

Abstract

The self-assembly kinetics for a norovirus capsid protein were probed by time-resolved small-angle X-ray scattering and then analyzed by singular value decomposition and global fitting. Only three species contribute to the total scattering intensities: dimers, intermediates comprising some 11 dimers, and icosahedral T = 3 capsids made up of 90 dimers. Three-dimensional reconstructions of the intermediate robustly show a stave-like shape consistent with an arrangement of two pentameric units connected by an interstitial dimer. Upon triggering of self-assembly, the biphasic kinetics consist of a fast step in which dimers are assembled into intermediates, followed by a slow step in which intermediates interlock into capsids. This simple kinetic model reproduces experimental data with an excellent agreement over 6 decades in time and with nanometer resolution. The extracted form factors are robust against changes in experimental conditions. These findings challenge and complement currently accepted models for the assembly of norovirus capsids.

The Structural Biology of Hepatitis B Virus: Form and Function

“…While HBV is relatively simple, virus assembly reactions can be much more complex involving an array of metastable intermediates (137, 138). The importance of the nucleation step is that it prevents formation of kinetic traps, reactions where incomplete capsids accumulate but there are not enough subunits to complete them.…”

Solution scattering from colloidal curved plates: barrel tiles, scrolls and spherical patches

“…The first case applies to the rolled-up nanoplatelets discussed above, while the second one can describe, for instance, the intermediates that make up a viral capsid (Tresset et al, 2013;Law-Hine et al, 2015).…”

Nanofluidic Devices with 8 Pores in Series for Real-Time, Resistive-Pulse Analysis of Hepatitis B Virus Capsid Assembly

“…13–14 Experimental observations indicate that in some cases assembly involves specific intermediates (incomplete capsids), suggesting a limited number of assembly paths. 15–19 Thus, a key factor for the development of thermodynamic and kinetic models for virus capsid assembly is the better characterization of the assembly intermediate species.…”