TABLE 1 .
Cleavage products of the replicase polyproteins of HCoV-EMC/2012
| Cleavage product | Position in polyprotein pp1a/pp1aba |
Protein size (no. of amino acids) |
Putative functional domain(s)b |
|---|---|---|---|
| nsp1 | 1Met-Gly193 | 193 | |
| nsp2 | 194Asp-Gly853 | 660 | |
| nsp3 | 854Ala-Gly2740 | 1887 | ADRP, PL2pro, TM1 |
| nsp4 | 2741Ala-Gln3247 | 507 | TM-2 |
| nsp5 | 3248Ser-Gln3553 | 306 | 3CLpro |
| nsp6 | 3554Ser-Gln3845 | 292 | TM-3 |
| nsp7 | 3846Ser-Gln3928 | 83 | |
| nsp8 | 3929Ala-Gln4127 | 199 | Putative primase |
| nsp9 | 4128Asn-Gln4237 | 110 | |
| nsp10 | 4238Ala-Gln4377 | 140 | |
| nsp11 | 4378Ser-Leu4391 | 14 | |
| nsp12 | 4378Ser-Gln5310 | 933 | RdRp |
| nsp13 | 5311Ala-Gln5908 | 598 | ZD, HEL1 |
| nsp14 | 5909Ser-Gln6432 | 524 | ExoN, NMT |
| nsp15 | 6433Gly-Gln6775 | 343 | NendoU |
| nsp16 | 6776Ala-Arg7078 | 303 | OMT |
Amino acids of the replicase proteins pp1a and pp1ab were numbered with the assumption that a −1 ribosomal frameshift occurs to express ORF1b, as in other coronaviruses (see text); the use of the slippery sequence UUUAAAC is predicted to result in a peptide bond between Asn4385 and Arg4386 in pp1ab.
The major transmembrane domains and a selection of the most conserved domains with enzymatic activities that have been characterized functionally and/or structurally in coronaviruses are listed. Abbreviations: PL2pro, papain-like proteinase 2; ADRP, ADP-ribose 1″-phosphatase; TM, transmembrane domain; 3CLpro, 3C-like cysteine proteinase; RdRp, RNA-dependent RNA polymerase; ZD, putative zinc-binding domain; HEL1, superfamily 1 helicase; ExoN, 3′-to-5′ exonuclease; NMT, N7-methyltransferase; NendoU, nidoviral endoribonuclease specific for U; OMT, S-adenosylmethionine-dependent ribose 2′-O-methyltransferase.