(a) Coomassie-stained SDS–PAGE analysis of FleN purified by GST column chromatography. Lane 1, marker; lane 2, target protein eluted from the GST column; lane 3, FleN after digestion of the GST tag; lane 4, wash with buffer A; lane 5, flowthrough after the supernatant had been loaded onto the column; lane 6, wash with buffer B. The molecular weights of the marker are shown in kDa on the left and the molecular weight of FleN is 30 kDa. (b) Coomassie-stained SDS–PAGE analysis of FleN after elution from the gel-filtration column. Lane 1, pure FleN; lane 2, marker.