title: Analysis in Escherichia coli of Plasmodium falciparum dihydropteroate synthase (DHPS) alleles implicated in resistance to sulfadoxine.
abstract: Mutations in Plasmodium falciparum dihydropteroate synthase have been linked to resistance to the antimalarial drug, sulfadoxine, which competes with the dihydropteroate synthase substrate, p-aminobenzoate. In an effort to evaluate the role of these mutations in a simple model system, we have expressed six relevant alleles of the P. falciparum dihydropteroate synthase gene in Escherichia coli. When each construct was produced in a dihydropteroate synthase disrupted E. coli strain that required thymidine, the thymidine requirement was lost, indicating heterologous complementation had occurred. In the presence of sulfadoxine, the growth of the strain with the wild-type dihydropteroate synthase allele was inhibited while those containing each of the five mutant alleles grew, indicating that these mutations can confer sulfadoxine resistance in E. coli. When tested against twelve additional 'sulfa' drugs a variety of responses were obtained. All strains were resistant to sulfadiazine, but the wild-type allele conferred sensitivity to all other sulfa drugs. Three alleles conferred resistance to dapsone, a drug that is to be targetted for a new regime of malaria treatment in Africa. All mutant alleles remained sensitive to sulfachloropyridazine and sulfacetamide. These results suggest new drugs that could be tried for effective malaria treatment.
authors.affiliation: Biomolecular Research Institute, CSIRO Health Sciences and Nutrition, 343 Royal Parade, Parkville, Vic. 3052, Australia.
authors.forename: Janette
authors.initials: J
authors.lastname: Berglez
authors.forename: Peter
authors.initials: P
authors.lastname: Iliades
authors.forename: Worachart
authors.initials: W
authors.lastname: Sirawaraporn
authors.forename: Peter
authors.initials: P
authors.lastname: Coloe
authors.forename: Ian
authors.initials: I
authors.lastname: Macreadie
mesh_terms: D000483:Alleles; D000818:Animals; D004094:Dihydropteroate Synthase / Q000235:genetics / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000201:enzymology; D015870:Gene Expression; D006801:Humans; D020128:Inhibitory Concentration 50; D008288:Malaria / Q000188:drug therapy*; D009154:Mutation; D010963:Plasmodium falciparum / Q000201:enzymology*; D013413:Sulfadoxine
chemical_list: D013413:Sulfadoxine; D004094:Dihydropteroate Synthase