Please use this identifier to cite or link to this item:http://hdl.handle.net/20.500.12105/6619
Acquisition of functions on the outer capsid surface during evolution of double-stranded RNA fungal viruses
PLoS Pathog. 2017 Dec 8;13(12):e1006755.
Unlike their counterparts in bacterial and higher eukaryotic hosts, most fungal viruses are transmitted intracellularly and lack an extracellular phase. Here we determined the cryo-EM structure at 3.7 Å resolution of Rosellinia necatrix quadrivirus 1 (RnQV1), a fungal double-stranded (ds)RNA virus. RnQV1, the type species of the family Quadriviridae, has a multipartite genome consisting of four monocistronic segments. Whereas most dsRNA virus capsids are based on dimers of a single protein, the ~450-Å-diameter, T = 1 RnQV1 capsid is built of P2 and P4 protein heterodimers, each with more than 1000 residues. Despite a lack of sequence similarity between the two proteins, they have a similar α-helical domain, the structural signature shared with the lineage of the dsRNA bluetongue virus-like viruses. Domain insertions in P2 and P4 preferential sites provide additional functions at the capsid outer surface, probably related to enzyme activity. The P2 insertion has a fold similar to that of gelsolin and profilin, two actin-binding proteins with a function in cytoskeleton metabolism, whereas the P4 insertion suggests protease activity involved in cleavage of the P2 383-residue C-terminal region, absent in the mature viral particle. Our results indicate that the intimate virus-fungus partnership has altered the capsid genome-protective and/or receptor-binding functions. Fungal virus evolution has tended to allocate enzyme activities to the virus capsid outer surface.
Amino Acid Sequence | Capsid | Capsid Proteins | Conserved Sequence | Cryoelectron Microscopy | Evolution, Molecular | Imaging, Three-Dimensional | Mutagenesis, Insertional | Protein Conformation, alpha-Helical | Protein Conformation, beta-Strand | Protein Interaction Domains and Motifs | Protein Multimerization | Protein Stability | RNA Viruses | Sequence Alignment | Structural Homology, Protein | Surface Properties | Virion | Xylariales | Models, Molecular
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