title: The antimalarial drug resistance protein Plasmodium falciparum chloroquine resistance transporter binds chloroquine.
abstract: Recently, mutations in the novel polytopic integral membrane protein PfCRT were shown to cause chloroquine resistance (CQR) in the malarial parasite Plasmodium falciparum. PfCRT is not a member of the well-known family of ABC proteins that have previously been associated with other drug resistance phenomena. Thus, the mechanism(s) whereby mutant PfCRT molecules confer antimalarial drug resistance is (are) unknown. Previously, we succeeded in overexpressing PfCRT to high levels in Pichia pastoris yeast by synthesizing a codon-optimized version of the pfcrt gene. Using purified membranes and inside-out plasma membrane vesicles (ISOV) isolated from strains harboring either wild-type or CQR-associated mutant PfCRT, we now show that under deenergized conditions the PfCRT protein specifically binds the antimalarial drug chloroquine (CQ) with a K(D) near 400 nM but does not measurably bind the related drug quinine (QN) at physiologically relevant concentrations. Transport studies using ISOV show that QN is passively accumulated as expected on the basis of previous measurement of the ISOV DeltapH for the different strains. However, passive accumulation of CQ is lower than expected for ISOV harboring mutant PfCRT, despite higher DeltapH for these ISOV.
authors.affiliation: Department of Chemistry, Lombardi Cancer Center, Georgetown University Medical Center, 3900 Reservoir Road, Washington, DC 20057, USA.
authors.forename: Hanbang
authors.initials: H
authors.lastname: Zhang
authors.forename: Michelle
authors.initials: M
authors.lastname: Paguio
authors.forename: Paul D
authors.initials: PD
authors.lastname: Roepe
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000737:chemistry; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002738:Chloroquine / Q000737:chemistry* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D009154:Mutation; D010843:Pichia / Q000378:metabolism; D010963:Plasmodium falciparum / Q000378:metabolism*; D011485:Protein Binding; D015800:Protozoan Proteins; D011803:Quinine / Q000737:chemistry; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors
chemical_list: D000962:Antimalarials; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D015800:Protozoan Proteins; D002738:Chloroquine; D011803:Quinine