A. SDS-PAGE gels show aliquots at different steps during the purification. Cell lysate–right after step C2 of purification, Supernatant–supernatant at step C3, His beads flow-through–flow-through at step C5, His beads elution–elution at step C5, Flag beads flow through–flow through of flag beads at step C6, Flag beads elution–elution at step 7. B. Two gels are fractions off MonoQ 10/100GL column and size exclusion column runs.