Fig. 1.
Cell-free cleavage activity of recombinant SARS-CoV 3CLpro. (A) The purified 3CLpro recombinant protein at the 1 mg/ml was analyzed by 10% SDS–PAGE with Coomassie blue staining (lane 2). (B) The trans-cleavage of the 3CLpro with a substrate fusion protein was determined using the ELISA. The substrate fusion protein was captured with anti-HSV mAb, followed by incubation with the serial dilution of the 3CLpro. The non-cleavage of the fusion protein was detected using the S protein-HRP conjugate and ABTS/H2O2 substrates. The ELISA product was measured at A405 nm. The relative cell-free cleavage activity was calculated as .