Production of water-soluble FMDV capsid protein complexes. (A) Dual SUMO fusion protein expression vectors for simultaneous expression of His6-Smt3-VP0, His6-Smt3-VP1 and His6-Smt3-VP3. The two vectors were transformed into BL21(DE3)-RIL E. coli cells, and selected by ampicillin (Ampr) and kanamycin resistance (Kanr). (B) SDS-PAGE of the purified capsid protein complexes without (left lane) or with (right lane) Ulp1 protease treatment. (C) Gel filtration. Purified capsid protein complexes were layered onto a size exclusion column (HiLoad 16/60 Superdex, GE Healthcare), and eluted at 1.0 ml/min. The elution volume is indicated. Values shown here are the established MWtheo. of commercial globular protein standards, and the computed MWapp. of capsid protein complexes from the plot.