| Abstract
| - The C-terminal nucleotide-binding domain (NBD2) of a P-glycoprotein-like transporter, encodedby the ltrmdr1 gene in Leishmania tropica and involved in parasite multidrug resistance (MDR), wasoverexpressed in Escherichia coli as a hexahistidine tagged protein and purified. The L. tropica recombinantdomain efficiently bound fluorescent derivatives of ATP, the hydrophobic steroid analogue RU 486, anddifferent classes of flavonoids with the following efficiency: flavone > flavanone > isoflavone >glucorhamnosyl-flavone > chromone. The affinity for flavones was dependent on the presence of hydroxylgroups at positions 5 and 3 and was further increased by a hydrophobic 1,1-dimethylallyl substituent atposition 8. When flow cytometry was used to measure daunomycin accumulation in a MDR L. tropicaline, a reversing effect was observed with flavones such as dimethylallyl-kaempferide at low concentrationor apigenin at higher concentration, but neither with the glucorhamnosyl derivative rutin nor with theisoflavone genistein. The in vivo reversing effect of dimethylallyl-kaempferide was correlated to a highinhibition of MDR cell growth in the presence of daunomycin. The results suggest that flavone inhibitionof both daunomycin efflux and parasite growth in the presence of the drug correlates to direct binding ofthe compound to cytosolic domain of the P-glycoprotein-like transporter.
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