Membrane-related processes and overall energy metabolism inTrypanosoma brucei and other kinetoplastid species

Abstract

An electrochemical proton gradient exists across the plasma membrane and the mitochondrial membrane of the bloodstream form ofTrypanosoma brucei. The membrane potential across the plasma membrane and the regulation of the internal pH depend on the temperature.Leishmania donovani regulates its internal pH and maintains a constant electrochemical proton gradient across its plasma membrane under all conditions examined. The mitochondrion of theT. brucei bloodstream form is energized, even though the reactions taking place in it do not result in net ATP synthesis and the Kreb's cycle and the respiratory chain are absent. Glucose is transported across the plasma membrane ofT. brucei by a facilitated diffusion carrier, that can transport a wider range of substrates than its mammalian counterparts. Pyruvate exits the cell via a facilitated diffusion transporter as well. Conflicting evidence exists for the mechanism of glucose transport inL. donovani; biochemical evidence suggests proton/glucose symport, while facilitated diffusion is indicated by physiological data.