FIG. 4.

Expression of MBP-Sao fusion protein in E. coli XL1-Blue and purification of recombinant mature Sao. A Coomassie-stained gel (A) and Western blot analysis (B) of the corresponding samples probed with convalescent-phase swine sera show the E. coli whole-cell lysate before (lane 1) and after (lane 2) induction with IPTG, the supernatant of the E. coli lysate (lane 3), the affinity-purified MBP-Sao fusion protein (lane 4), Sao and MBP cleaved by factor Xa (lane 5), and recombinant Sao devoid of MBP purified by anion-exchange chromatography (lane 6). The molecular masses are indicated on the left.