The Plasma Membrane H + -ATPase of Leishmania donovani Promastigotes

The trypanosomatid protozoan Leishmania has a digenetic life cycle in which both developmental stages are continuously exposed to harsh environments, first as extracellular flagellated promastigote forms in the alimantary tract of their sandfly vectors and subsequently as obligate intracellular amastigote forms within phagolysosomal compartments of mammalian macrophages (Chang and Dwyer 1978, Dwyer 1979). The adaptive mechanisms by which these organisms survive in the widely different environmental conditions are still largely unknown but obviously involve surface interactions since all physiologic and biochemical interactions occur across such membranes. Previously, we have demonstrated that L. donovani possess active transport systems which are proton motive force driven (pmf), i.e. a proton electrochemical gradient (Δµ H+) is created across the parasite surface membrane which is coupled to transport systems by maintaining symport translocation of the specific substrate with protons (Zilberstein and Dwyer 1985). Such a Δµ H+ is composed of a chemical gradient (ΔpH) and of membrane potential (Δψ). The size of the electrical membrane potential across L. donovani promastigote plasma membranes was recently determined to be 90 mV. Furthermore, a direct correlation between the size of the Δµ H+ and the transport of L-proline have been demonstrated (Zilberstein, Langley and Dwyer, Submitted for publication).