FIG. 4.
Velcade does not inhibit SARS-CoV main protease activity. A fluorimetric SARS-CoV nsp5 protease activity assay (see Materials and Methods) was performed. (A) Change in fluorescence as a result of cleavage of a Dabcyl-VRLQSGTC-fluorescein peptide substrate by wild-type nsp5 or an active site mutant (nsp5C145A) in the presence or absence of 50 μM Velcade. Symbols: □, wild-type nsp5; ○, wild-type nsp5 + Velcade; ▾, nsp5C145A. (B) Cleavage rate for wild-type nsp5 in the absence or presence of different concentrations of Velcade.