The distribution of permeant ions demonstrates the presence of at least two distinct electrical gradients in bloodstream forms of Trypanosoma brucei.
The distribution of 86Rb+ and the radiolabelled lipophilic cation [3H]methyltriphenylphosphonium (MePh3P+) was used to investigate the membrane potentials that exist in bloodstream forms of Trypanosoma brucei. Even after correction for binding to cellular constituents, the accumulation of MePh3P+ was approximately tenfold greater than the accumulation of Rb+ under resting conditions. The addition of low concentrations of carbonylcyanide p-trifluoromethoxyphenylhydrazone or valinomycin reduced the accumulation of MePh3P+ tenfold without perturbing the accumulation of Rb+. Although selective permeabilization of the plasma membrane abolished the accumulation of Rb+ and caused a substantial decrease in the accumulation of MePh3P+, a significant carbonylcyanide-p-trifluoromethoxyphenylhydrazone-sensitive accumulation of MePh3P+ persisted under these conditions. These data were consistent with the presence of at least two distinct membrane potentials (delta psi) in bloodstream forms of T. brucei; a potential across the plasma membrane (delta psi p) and an additional delta psi, generated by the electrogenic movement of H+, across the membrane of an intracellular organelle that possesses no electrical permeability to Rb+ or K+.
Nolan
D P
DP
Department of Biochemistry, Trinity College, Dublin, Ireland.
Voorheis
H P
HP
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002463:Cell Membrane Permeability; D007202:Indicators and Reagents; D008564:Membrane Potentials; D009861:Onium Compounds / Q000378:metabolism; D009994:Osmolar Concentration; D051381:Rats; D012413:Rubidium / Q000378:metabolism; D014320:Triphenylmethyl Compounds / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D014634:Valinomycin / Q000494:pharmacology
D007202:Indicators and Reagents; D009861:Onium Compounds; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D014634:Valinomycin; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000255:Adenosine Triphosphate; D012413:Rubidium