The plasmid pGEX-T2b was constructed via two steps: amplifying the PCR fragments first and then cloning the PCR fragments into appropriate vectors (as above). PGEX-T2b was transformed into E. coli BL21 (DE3). Protein expression was induced with 0.1 mM IPTG (isopropyl-b-D-thiogalactopyranoside). Purification of the protein was carried out using glutathione beads. The cleavage of GST/TAV2b protein was carried out using thrombin (Novagen) as recommended by the manufacturer. The purity of the purified protein was analysed by SDS-PAGE. The amount of purified protein was measured using the Bio-Rad protein assay.