Figure 2.

Effect of isotuberculosinol on maturation of macrophage phagosomes containing control (−) or isotuberculosinol coated (+) beads, as indicated by solid and dotted lines, respectively. (a) Effect on pH. (b) Effect on proteolytic activity. Reprinted with permission from Ref. [25]. Copyright 2009 American Chemical Society. As indicated by the arrows, the effect on pH is observable within ~10 min., while that on proteolysis is only observed after ~20 min. The increase in proteolysis observed in the negative control phagosome presumably reflects its fusion with a protease containing lysosome. We hypothesize that, rather than reflecting a distinct effect, the latter occurring blockage of lysosomal fusion is a result of incomplete acidification.