FIG. 6.
BFT purified by a urea-based modified method. (A) Profile of eluted BFT-2 from urea-based Mono Q anion-exchange chromatography. Far left arrow indicates the sharp peak of BFT-2 eluted at 0.18 M NaCl in the presence of 6 M urea. This compares with the broader elution peak observed using the Van Tassell purification method and shown in Fig. 1B. (B) Western blot of urea-based Mono Q peaks. Peaks indicated by arrows were analyzed by Western blot analysis using polyclonal BFT-2 antiserum (1/1,000 dilution). Both peaks were treated with proteinase K as described in the text. Lane 1, BFT-2 fraction; lane 2, BFT-2 fraction after proteinase K treatment; lane 3, peak 2; lane 4, peak 2 after proteinase K treatment. Proteinase K treatment eliminated the BFT-2 peak but did not alter the higher-molecular-mass peaks shown in lanes 3 and 4. (C) Silver stain of BFT-2 after purification by urea-based Mono Q anion-exchange chromatography and SDS-PAGE electrophoresis. Lane 1, molecular weight markers; lane 2, BFT-2 (200 ng of protein).