title: A critical role for PfCRT K76T in Plasmodium falciparum verapamil-reversible chloroquine resistance.
abstract: Chloroquine resistance (CQR) in Plasmodium falciparum is associated with mutations in the digestive vacuole transmembrane protein PfCRT. However, the contribution of individual pfcrt mutations has not been clarified and other genes have been postulated to play a substantial role. Using allelic exchange, we show that removal of the single PfCRT amino-acid change K76T from resistant strains leads to wild-type levels of CQ susceptibility, increased binding of CQ to its target ferriprotoporphyrin IX in the digestive vacuole and loss of verapamil reversibility of CQ and quinine resistance. Our data also indicate that PfCRT mutations preceding residue 76 modulate the degree of verapamil reversibility in CQ-resistant lines. The K76T mutation accounts for earlier observations that CQR can be overcome by subtly altering the CQ side-chain length. Together, these findings establish PfCRT K76T as a critical component of CQR and suggest that CQ access to ferriprotoporphyrin IX is determined by drug-protein interactions involving this mutant residue.
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Lakshmanan
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Bray
authors.forename: Dominik
authors.initials: D
authors.lastname: Verdier-Pinard
authors.forename: David J
authors.initials: DJ
authors.lastname: Johnson
authors.forename: Paul
authors.initials: P
authors.lastname: Horrocks
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Muhle
authors.forename: George E
authors.initials: GE
authors.lastname: Alakpa
authors.forename: Ruth H
authors.initials: RH
authors.lastname: Hughes
authors.forename: Steve A
authors.initials: SA
authors.lastname: Ward
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Krogstad
authors.forename: Amar Bir Singh
authors.initials: AB
authors.lastname: Sidhu
authors.forename: David A
authors.initials: DA
authors.lastname: Fidock
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D002738:Chloroquine / Q000494:pharmacology*; D004351:Drug Resistance / Q000187:drug effects*; D006427:Hemin / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009154:Mutation; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D000962:Antimalarials; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D015800:Protozoan Proteins; D006427:Hemin; D002738:Chloroquine; D014700:Verapamil