Capsid protein alpha self-assembles to form an icosahedral procapsid with a T=3 symmetry, about 30 nm in diameter, and consisting of 60 capsid proteins trimers. In addition, 240 calcium ions are incorporated per capsid during assembly. The capsid encapsulates the two genomic RNAs. Capsid maturation occurs via autoproteolytic cleavage of capsid protein alpha generating capsid protein beta and the membrane-active peptide gamma. Membrane-permeabilizing peptide produced by virus maturation, thereby creating the infectious virion. After endocytosis into the host cell, peptide gamma is probably exposed in endosomes, where it permeabilizes the endosomal membrane, facilitating translocation of viral capsid or RNA into the cytoplasm (Probable). Hydrolysis of an asparaginyl bond involved in the maturation of the structural protein of the virus, typically -Asn-|-Ala- or -Asn-|-Phe-. Located inside the capsid and probably externalized in early endosomes. Capsid protein alpha autocatalytically maturates into capsid protein beta and peptide gamma. Belongs to the peptidase A6 family. Icosahedral capsid structure