Values for dN/dS of amino acid sites in relation to domain functions in astrovirus ORF1a (A), ORF1b (B) and ORF2 (C). For each site, the BEB-derived value of dN/dS (Y-axis) is plotted against the position of the residue in the polyprotein encoded by the ORF (X-axis). Arrows and scale bars indicate sites proposed for proteolytic digestion and predicted for phosphorylation (T, Y and S in ORF1b) as well as domain functions described in publications or predicted by servers. Numbering is according to human astrovirus serotype 1 Z25771. 3A: CC: coiled coil, TMH: transmembrane helix Nsp1a: non-structural protein 1a. 1: Region putatively involved in viral RNA helicase activity (1–80). 2: Protease domain (447–589). 3: Reported death domain and nuclear localization signal (620–714). 4: Hypervariable region and cell-growth induced deletion (760–838). 5: Ribosomal frameshifting signal (918–935). 6: Variable region prone to O-glycosylation and phosphorylation (608–632). 7: Putative VPg region associated with viral RNA replication (664–757). 8: KKXX-like ER retention (931–934). 3B: 1: Ribosomal frameshifting signal (1–28). 2: Predicted furin-type cleavage site (32–38). 3: Conserved polymerase domain (...-...). 3C: Rxxx: Arg-residues reported to mark tryptic digestion. T227: Thr-residue reported to bind viral RNA. 1a & 1b: NGR, RGD-like cell attachment motif (16–52). 2: LDV, RGD-like cell attachment motif (182–184). 3: Reported common epitope (340–376). 4: RGD: integrin recognition motif for cell attachment (572–574). 5: Predicted serotypic epitope (580–606). 6: Region of intracellular caspase digestion (701–787). 7: Region of extracellular tryptic digestion (300–423). 8, 9, 10: VP34, VP27, VP25, viral capsid proteins.