Comparison of ORFs and protein domains across nidovirus groups, illustrating the genome architecture of arteriviruses (equine arteritis virus), mesoniviruses (Nam Dinh virus), coronaviruses (SARS-CoV), and planarian secretory cell nidovirus (PSCNV), the nidovirus with the largest known genome size at 41.1kb. Novel domains present in PSCNV are included.

Original caption: Fig 2. Genomes and proteomes of nidoviruses.

ORFs and encoded protein domains in genomes of viruses representing three nidovirus families and PSCNV. The protein-encoding part of the genomes is split in three adjacent regions, which are colored and labelled accordingly. EAV, equine arteritis virus; NDiV, Nam Dinh virus; SARS-CoV (see S1 Table for details on these viruses). ORF1a frame is set as zero. Protein domains conserved between these nidoviruses and PSCNV, and those specific to PSCNV are shown. TM, transmembrane domain (TM helices are shown by black bars above TM domains); Tandem repeats, two adjacent homologous regions of unknown function; RNase T2, ribonuclease T2 homolog; 3CLpro, 3C-like protease; NiRAN, nidovirus RdRp-associated nucleotidyltransferase; RdRp, RNA-dependent RNA polymerase; HEL1, superfamily 1 helicase with upstream Zn-binding domain (ZBD); ExoN, DEDDh subfamily exoribonuclease; N-MT and O-MT, SAM-dependent N7- and 2’-O-methyltransferases, respectively; Thr-rich, region enriched with Thr residue; FN2a/b, fibronectin type 2 domains; ANK, ankyrin domain.