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Betacoronavirus SUD-C domain This domain is found in betacoronavirus non-structural protein NSP3, and is about 65 amino acids in length. It was originally thought to exist only in SARS-coronaviruses, and so was termed the SARS-unique domain (SUD), however this has since been shown to be incorrect. The NSP3 is the product of ORF1a, proteolytically released from the pp1a/1ab polyprotein. The SUD domain has three globular domains, SUD-N (N-terminal), SUD-M (middle region of SUD), and SUD-C (C-terminal). SUD-C adopts a fold consisting of seven beta-strands arranged in an anti-parallel beta-sheet, and two alpha-helices which are packed against the same side of the beta-sheet. It adopts a frataxin-like fold with structural similarities to DNA-binding domains. It has been shown that SUD-C binds to single-stranded RNA and recognises purine bases more strongly than pyrimidine bases, but these interactions are stabilised in the presence of SUD-M. The function of this domain is not clear but studies of structural homologues of SUD-C suggest that it could be related to metal, adenylate and nucleic acid binding. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",