title: On the molecular mechanism of chloroquine's antimalarial action.
abstract: Chloroquine is thought to exert its antimalarial effect by preventing the polymerization of toxic heme released during proteolysis of hemoglobin in the Plasmodium digestive vacuole. The mechanism of this blockade has not been established. We incubated cultured parasites with subinhibitory doses of [3H]chloroquine and [3H] quinidine. These [3H]quinoline compounds became associated with hemozoin as assessed by electron microscope autoradiography and subcellular fractionation. In vitro, binding of [3H]quinoline inhibitors to the hemozoin chain depended on the addition of heme substrate. These data counter previous conclusions regarding the lack of quinoline association with hemozoin, explain the exaggerated accumulation of quinolines in the plasmodium digestive vacuole, and suggest that a quinoline heme complex incorporates into the growing polymer to terminate chain extension, blocking further sequestration of toxic heme.
authors.affiliation: Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, MO USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Sullivan
authors.forename: I Y
authors.initials: IY
authors.lastname: Gluzman
authors.forename: D G
authors.initials: DG
authors.lastname: Russell
authors.forename: D E
authors.initials: DE
authors.lastname: Goldberg
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000378:metabolism / Q000494:pharmacology*; D002738:Chloroquine / Q000378:metabolism / Q000494:pharmacology*; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology*; D006418:Heme / Q000378:metabolism; D006420:Hemeproteins / Q000096:biosynthesis / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008961:Models, Structural; D010963:Plasmodium falciparum / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D011506:Proteins / Q000378:metabolism; D015800:Protozoan Proteins / Q000378:metabolism; D011804:Quinolines / Q000378:metabolism; D014617:Vacuoles / Q000502:physiology / Q000648:ultrastructure; D000099053:Histidine-Rich Glycoprotein
chemical_list: D000962:Antimalarials; D006420:Hemeproteins; D011506:Proteins; D015800:Protozoan Proteins; D011804:Quinolines; D000099053:Histidine-Rich Glycoprotein; C020753:hemozoin; D006418:Heme; D002738:Chloroquine; C037219:quinoline