When viruses are viewed as dynamic containers of an infectious genome, their structural, physical, and biochemical analyses become necessary to understand the molecular mechanisms that control their successful life cycle. Information on virus structures at the highest possible resolution is essential for identifying the principles of their structure-function relationship, and could lead to development of antivirals, vaccines, and the advancement of new platforms for virus-based nanotechnology.

   Three-dimensional cryogenic electron microscopy (cryo-EM), which has revolutionized structural biology, is central to determining high-resolution structures of many viral assemblies in near-native conditions. We use Cryo-EM to solve near-atomic structures of infectious virions with helical or icosahedral symmetry. State-of-the-art approaches now extend beyond purified symmetric capsids and focus on the asymmetric components as the genome and viral polymerases. Asymmetric structures have important functions in many steps of the virus replication cycle, and many of these will be key targets for the development of new antiviral drugs.

   Our group studies several viruses with varying levels of complexity, with focus on a number of double-stranded RNA viruses such as infectious bursal disease virus, the human picobirnavirus, and several fungal viruses (Saccharomyces cerevisiae virus L-A, Penicillium chrysogenum virus, and Yadonushivirus), as well as single-stranded RNA viruses such as human rhinovirus and rabbit hemorrhagic disease virus. We extended our studies to other macromolecular assemblies such as α2-macroglobulin, a blood plasma proteinase inhibitor of broad specificity, and encapsulins, bacterial nanocages that naturally confine a functional protein cargo such as an enzyme. Structural analysis is complemented by study of mechanical properties by atomic force microscopy (AFM), to examine the relationship between physical properties such as rigidity and mechanical resilience, and virus biological function.

   Finally, our research establishes the basis for incorporation of heterologous proteins and/or chemicals into viral capsids, considered as nanocontainers or nanocarriers, of potential use for future biotechnological applications.

  

   The Castón group gratefully acknowledges support throughout the years from

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