Oxidative phosphorylation, Ca2+ transport, and fatty acid-induced uncoupling in malaria parasites mitochondria

Respiration, oxidative phosphorylation, calcium uptake, and the mitochondri al membrane potential of trophozoites of the malaria parasite Plasmodium be rghei were assayed in situ after permeabilization with digitonin, ADP promo ted an oligomycin-sensitive transition from resting to phosphorylating resp iration. Respiration was sensitive to antimycin A and cyanide. The capacity of trophozoites to sustain oxidative phosphorylation was additionally supp orted by the detection of an oligomycin-sensitive decrease in mitochondrial membrane potential induced by ADP, Phosphorylation of ADP could be obtaine d in permeabilized trophozoites in the presence of succinate, citrate, alph a-ketoglutarate, glutamate, malate, dihydroorotate, alpha-glycerophosphate, and N,N,N',N'-tetramethyl-p-phenylenediamine Ca2+ uptake caused membrane d epolarization compatible with the existence of an electrogenically mediated Ca2+ transport system in these mitochondria, An uncoupling effect of fatty acids was partly reversed by bovine serum albumin, ATP, or GTP and not aff ected by atractyloside, ADP, glutamate, or malonate, Evidence for the prese nce of a mitochondrial uncoupling protein in P, berghei was also obtained b y using antibodies raised against plant uncoupling mitochondrial protein. T ogether these results provide the first direct biochemical evidence of mito chondrial function in ATP synthesis and Ca2+ transport in a malaria parasit e and suggest the presence of an H+ conductance in trophozoites similar to that produced by a mitochondrial uncoupling protein.