title: Plasmodium falciparum chloroquine resistance transporter (PfCRT) isoforms PH1 and PH2 perturb vacuolar physiology.
abstract: BACKGROUND
  Recent work has perfected yeast-based methods for measuring drug transport by the Plasmodium falciparum chloroquine (CQ) resistance transporter (PfCRT).
  
  
  METHODS
  The approach relies on inducible heterologous expression of PfCRT in Saccharomyces cerevisiae yeast. In these experiments selecting drug concentrations are not toxic to the yeast, nor is expression of PfCRT alone toxic. Only when PfCRT is expressed in the presence of CQ is the growth of yeast impaired, due to inward transport of chloroquine (CQ) via the transporter.
  
  
  RESULTS
  During analysis of all 53 known naturally occurring PfCRT isoforms, two isoforms (PH1 and PH2 PfCRT) were found to be intrinsically toxic to yeast, even in the absence of CQ. Additional analysis of six very recently identified PfCRT isoforms from Malaysia also showed some toxicity. In this paper the nature of this yeast toxicity is examined. Data also show that PH1 and PH2 isoforms of PfCRT transport CQ with an efficiency intermediate to that catalyzed by previously studied CQR conferring isoforms. Mutation of PfCRT at position 160 is found to perturb vacuolar physiology, suggesting a fitness cost to position 160 amino acid substitutions.
  
  
  CONCLUSIONS
  These data further define the wide range of activities that exist for PfCRT isoforms found in P. falciparum isolates from around the globe.
authors.affiliation: Department of Chemistry, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA.|Department of Biochemistry, Cellular and Molecular Biology, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Callaghan
authors.affiliation: Department of Chemistry, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA.|Department of Biochemistry, Cellular and Molecular Biology, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA.
authors.forename: Amila
authors.initials: A
authors.lastname: Siriwardana
authors.affiliation: Department of Chemistry, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA.|Department of Biochemistry, Cellular and Molecular Biology, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Hassett
authors.affiliation: Department of Chemistry, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA. roepep@georgetown.edu.|Department of Biochemistry, Cellular and Molecular Biology, Georgetown University, 37th and O Streets, NW, Washington, DC, 20057, USA. roepep@georgetown.edu.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Roepe
mesh_terms: D002738:Chloroquine / Q000378:metabolism; D008296:Malaysia; D026901:Membrane Transport Proteins / Q000235:genetics / Q000633:toxicity*; D020033:Protein Isoforms / Q000235:genetics / Q000633:toxicity*; D015800:Protozoan Proteins / Q000235:genetics / Q000633:toxicity*; D011994:Recombinant Proteins / Q000235:genetics / Q000633:toxicity*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D014617:Vacuoles / Q000502:physiology*
chemical_list: D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D020033:Protein Isoforms; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D002738:Chloroquine
keywords: Chloroquine resistance; Cytostatic; Drug transport