Cryo-EM reconstructions of BMV-derived virus-like particles reveal assembly defects in the icosahedral lattice structure

from the recombinant capsid protein of brome mosaic virus (BMV). The analysis of VLPs was performed by Cryo-EM reconstructions and allowed us to visualize a few classes of VLPs, giving insight into the VLP self-assembly process. Apart from the mature icosahedral VLP practically identical with native virions, we describe putative VLP intermediates displaying non-icosahedral arrangements of capsomers, proposed to occur before the final disorder-order transition stage of icosahedral VLP assembly. Some of the described VLP classes show a lack of protein shell continuity, possibly resulting from too strong interaction with the cargo (in this case tRNA) with the capsid protein. We believe that our results are a useful prerequisite for the rational design of VLPs in the future and lead the way to the effective production of modified VLPs.