Native-PAGE and zymogram of pure HhXyl. Samples of pure protein were loaded on two native gels (12%). (A) In the absence of xylan, the gel was stained with Coomassie brilliant blue R250 to visualize the band corresponding to xylanase (35.5 kDa). (B) In the presence of 2% xylan, the gel was stained with Congo red to verify the xylanase activity. The amounts of protein loaded were 2.5 μg (Lanes 2 and 4) and 5 μg (Lanes 3 and 5) are indicated on the figure. The molecular weight is indicated in kilodaltons (Lane 1).