The Roles of Electrostatic Interactions in Capsid Assembly Mechanisms of Giant Viruses.

In the last three decades, many giant DNA viruses have been discovered. Giant viruses present a unique and essential research frontier for studies of self-assembly and regulation of supramolecular assemblies. The question on how these giant DNA viruses assemble thousands of proteins so accurately to form their protein shells, the capsids, remains largely unanswered. Revealing the mechanisms of giant virus assembly will help to discover the mysteries of many self-assembly biology problems. Paramecium bursaria Chlorella virus-1 (PBCV-1) is one of the most intensively studied giant viruses. Here, we implemented a multi-scale approach to investigate the interactions among PBCV-1 capsid building units called capsomers. Three binding modes with different strengths are found between capsomers around the relatively flat area of the virion surface at the icosahedral 2-fold axis. Furthermore, a capsomer structure manipulation package is developed to simulate the capsid assembly process. Using these tools, binding forces among capsomers were investigated and binding funnels were observed that were consistent with the final assembled capsid. In addition, total binding free energies of each binding mode were calculated. The results helped to explain previous experimental observations. Results and tools generated in this work established an initial computational approach to answer current unresolved questions regarding giant virus assembly mechanisms. Results will pave the way for studying more complicated process in other biomolecular structures.

Visualization of giant virus particles and development of "VIRAMOS" for high school and university biology course.

Several educational trials on handling viruses and or virology have been reported. However, given their small size, direct visualization of these viruses under a microscope has been rarely performed. The so-called "giant viruses" are larger than other viruses with a particle size greater than 200-300 nm. This enables their direct visualization under a light microscope more easily than other viruses. In this study, we developed two new types of teaching material for learning about viruses and cellular organisms using mimivirus, one of the well-known giant viruses. One teaching material involves using glass slides with enclosed mimivirus particles, and another is a paper-based teaching material, named VIRAMOS (http://tlab-edusys.azurewebsites.net/content/viramos_en.pdf). Using these, students can investigate and learn about viruses and cellular organisms. © 2019 International Union of Biochemistry and Molecular Biology, 47(4):426-431, 2019.

The multiple origins of proteins present in tupanvirus particles.

In the last few decades, the isolation of amoebae-infecting giant viruses has challenged established principles related to the definition of virus, their evolution, and their particle structures represented by a variety of shapes and sizes. Tupanviruses are one of the most recently described amoebae-infecting viruses and exhibit a peculiar morphology with a cylindrical tail attached to the capsid. Proteomic analysis of purified viral particles revealed that virions are composed of over one hundred proteins with different functions. The putative origin of these proteins had not yet been investigated. Here, we provide evidences for multiple origins of the proteins present in tupanvirus particles, wherein 20% originate from members of the archaea, bacteria and eukarya.