Endosomal acidification defects in <i>phg1a</i> KO cells are not corrected by overexpression of Kil1.

<p>In order to measure the acidification of endosomal compartments, <i>Dictyostelium</i> cells were allowed to engulf fluid phase containing two dextran-coupled fluorescent markers, one sensitive to pH (Oregon Green 488), the other one not (Alexa 647). A) The calibration curve indicates the OG/Alexa 647 ratio obtained by imposing different endosomal pH (3.5 to 6.5). B) Kinetics of endosomal acidification in WT or mutant cells. The left axis indicates the OG/Alexa 647 ratio, the right axis the corresponding pH values. The average and S.E.M. of at least 3 independent experiments are presented.