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 ...
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 domain is also known as DPUP (domain preceding Ubl2 and PL2pro). NSP3 is the product of ORF1a, proteolytically released from the pp1a/1ab polyprotein [1,2]. 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 [3].