NTPase presumably plays a role in replication. Despite having similarities with helicases, does not seem to display any helicase activity (By similarity). Viral genome-linked protein is covalently linked to the 5'-end of the positive-strand, negative-strand genomic RNAs and subgenomic RNA. Acts as a genome-linked replication primer. May recruit ribosome to viral RNA thereby promoting viral proteins translation (By similarity). Protease-polymerase processes the polyprotein: Pro-Pol is first released by autocleavage, then all other proteins are cleaved. Protease-polymerase is an RNA-directed RNA polymerase which replicates genomic and antigenomic viral RNA by recognizing specific signals. Catalyzes the covalent attachment VPg with viral RNAs (By similarity). Capsid protein self assembles to form an icosahedral capsid with a T=3 symmetry, about 38 nm in diameter, and consisting of 180 capsid proteins. The capsid encapsulate the genomic RNA and VP2 proteins. Attaches virion to target cells, inducing endocytosis of the viral particle. Acidification of the endosome induces conformational change of capsid protein thereby injecting virus genomic RNA into host cytoplasm (By similarity). a ribonucleoside 5'-triphosphate + H2O = a ribonucleoside 5'-diphosphate + H(+) + phosphate a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Endopeptidase with a preference for cleavage when the P1 position is occupied by Glu-|-Xaa and the P1' position is occupied by Gly-|-Yaa. Homodimer. Homomultimer. Protease-polymerase is composed of two domains displaying two different catalytic activity. These activities may act independently. Specific enzymatic cleavages in vivo yield mature proteins. Pro-Pol is first autocatalytically cleaved, then processes the whole polyprotein. VPg is uridylylated by the polymerase and is covalently attached to the 5'-end of the polyadenylated genomic and subgenomic RNAs. This uridylylated form acts as a nucleotide-peptide primer for the polymerase (By similarity). Two different RNAs lead the expression of the capsid protein. One arises from the cleavage of the polyprotein translated from the genomic RNA and the other from the translation of a subgenomic RNA derived from the (-)RNA template. Capsid protein expressed from the subgenomic mRNA is produced in much larger amounts than the cleaved one (By similarity). Produced from the genomic RNA. Produced from the subgenomic RNA by alternative promoter usage. The N-terminal part of the polyprotein may be missing and the genome sequence may lack the 5'-end, since all other sapoviruses code for a supplemental N-terminal peptide.