Contains the viral protease participating in the cleavage of the polyprotein into functional products. It contains also the activities necessary for replication of genomic RNA, as well as transcription of subgenomic mRNA. Protein covalently attached to the 5' extremity of the genomic and subgenomic RNAs. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Cleaved presumably by viral and host proteases. Generated by a ribosomal frameshift at position 919. Belongs to the astroviridae polyprotein 1AB family.