Viruses with Single-Stranded, Positive-Sense RNA Genomes

Table 14.6 Functions and properties of astrovirus proteins

Protein	Molecular mass (kDa)	Reading frame	Function/properties
NSP1a/1	20	ORF1a	????
NSP1a/2	23	ORF1a	Hydrophobic, contains putative transmembrane domains
NSP1a/3	27	ORF1a	3C-like protease 3CL^pro, cleavage of precursor protein(s)
NSP1a/4	26–35	ORF1a	Contains nuclear transport signal, located in perinuclear region, associates with ER
NSP1b	≈57	ORF1b	RNA-dependent RNA polymerase, transcription, replication
pVP87	70–87	ORF2	Precursor protein of capsid proteins; different size in different virus types; cleaved by cellular typsin-like proteases
VP34	34	ORF2	Capsid protein, amino-terminal cleavage product of pVP87, conserved
VP26, VP29	26–29	ORF2	Capsid proteins, carboxy-terminal cleavage product of pVP87, variable; proteins are generated by alternative use of cleavage sites within pVP87, induction of neutralizing antibodies, substrate of cellular caspases

The protein succession order in the table corresponds to the real order of the reading frames in the genome and in the precursor proteins
ORF open reading frame, ER endoplasmic reticulum