Figure 2

Heparin and Mitoxantrone collectively reduce protease sensitivity of spike. (A) Either heparin or Mitoxantrone alone does not affect the protease sensitivity of spike. Spike ECD incubated with heparin (25 μM) or Mitoxantrone (25 μM) or with a buffer control was treated with increased concentrations of proteinase K for 10 min. The samples were analyzed by immunoblotting with spike antibodies. The graph shows the quantification of the S2 band in (A). (B) Heparin binding in the presence of Mitoxantrone increases the protease resistance of spike. As in (A), except that spike was treated with heparin and Mitoxantrone together before proteolysis. The graph shows the quantification of the S2 band in (B). n = 3 independent experiments. Error bars, S.E.M.