Selectivity in ISG15 and ubiquitin recognition by the SARS coronavirus papain-like protease

Arch Biochem Biophys. 2007 Oct 1;466(1):8-14. doi: 10.1016/ Epub 2007 Jul 14.


The severe acute respiratory syndrome coronavirus papain-like protease (SARS-CoV PLpro) carries out N-terminal processing of the viral replicase polyprotein, and also exhibits Lys48-linked polyubiquitin chain debranching and ISG15 precursor processing activities in vitro. Here, we used SDS-PAGE and fluorescence-based assays to demonstrate that ISG15 derivatives are the preferred substrates for the deubiquitinating activity of the PLpro. With k(cat)/K(M) of 602,000 M(-1)s(-1), PLpro hydrolyzes ISG15-AMC 30- and 60-fold more efficiently than Ub-AMC and Nedd8-AMC, respectively. Data obtained with truncated ISG15 and hybrid Ub/ISG15 substrates indicate that both the N- and C-terminal Ub-like domains of ISG15 contribute to this preference. The enzyme also displays a preference for debranching Lys48- over Lys63-linked polyubiquitin chains. Our results demonstrate that SARS-CoV PLpro can differentiate between ubiquitin-like modifiers sharing a common C-terminal sequence, and that the debranching activity of the PLpro is linkage type selective. The potential structural basis for the demonstrated specificity of SARS-CoV PLpro is discussed.

MeSH terms

  • Binding Sites
  • Coronavirus 3C Proteases
  • Cysteine Endopeptidases / chemistry*
  • Cytokines / chemistry*
  • Enzyme Activation
  • Protein Binding
  • Substrate Specificity
  • Ubiquitin / chemistry*
  • Ubiquitins / chemistry*
  • Viral Proteins / chemistry*


  • Cytokines
  • Ubiquitin
  • Ubiquitins
  • Viral Proteins
  • ISG15 protein, human
  • Cysteine Endopeptidases
  • Coronavirus 3C Proteases