The Toxoplasma gondii vacuolar proton ATPase
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Toxoplasma gondii is an opportunistic organism in immunocompromised patients and an important cause of congenital disease. Our laboratory identified a new compartment in T. gondii which has several proteins homologous to plant vacuolar proteins, including the vacuolar proton pyrophosphatase and subunits of the vacuolar proton ATPase (V-H+-ATPase). The V-H+-ATPase is an enzyme involved in vacuolar acidification and vesicle trafficking in eukaryotic cells and we hypothesize it serves similar roles in the parasite. Two a subunits were found in the T. gondii genome and named as TgVHA-a1 and TgVHA-a2. We demonstrated that TgVHA-a1 localizes to the PLV, whereas TgVHA-a2 is associated with the plasma membrane of extracellular tachyzoites. Our studies revealed a possible role for the V-H+-ATPase in the T. gondii secretory pathway as both a subunits colocalize with TgMIC2 in a TgVP1 knockout line.