FIGURE 1.

Distribution of V-ATPase isoforms, PIP lipids and the pH of subcellular organelles. Subcellular localization of isoforms of the 100 kDa a-subunit of the V-ATPase, in yeast and mammals, are indicated by separately coloring the a-subunit isoforms. The key to the respective a-subunit isoforms are indicated on the right side of the figure. On the left bottom, a key to the different organelles in the figure is present. The distinct enrichment of PIP lipids on the membranes of subcellular organelles and compartments are indicated by different colors. The key to the color-coded PIP species is on the bottom right side of the figure. Enrichment of PI(4)P is indicated in the compartments of the Golgi network and the plasma membrane. In addition to PI(4)P, the plasma membrane maintains an enrichment of PI(4,5)P₂ and PI(3,4,5)P₃. Secretory vesicles are also indicated to be enriched in PI(4)P. The endosomal compartments, including the early-, late- and recycling-endosomes and lysosomes, are characteristically enriched in PI(3)P. The late endosomes and lysosomes, in addition, maintains the highly regulated species PI(3,5)P₂. pH or pH-ranges of all the different organelles are indicated by numbers inside or beside the respective organelles.