title: Insights into antifolate resistance from malarial DHFR-TS structures.
abstract: Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) is an important target of antimalarial drugs. The efficacy of this class of DHFR-inhibitor drugs is now compromised because of mutations that prevent drug binding yet retain enzyme activity. The crystal structures of PfDHFR-TS from the wild type (TM4/8.2) and the quadruple drug-resistant mutant (V1/S) strains, in complex with a potent inhibitor WR99210, as well as the resistant double mutant (K1 CB1) with the antimalarial pyrimethamine, reveal features for overcoming resistance. In contrast to pyrimethamine, the flexible side chain of WR99210 can adopt a conformation that fits well in the active site, thereby contributing to binding. The single-chain bifunctional PfDHFR-TS has a helical insert between the DHFR and TS domains that is involved in dimerization and domain organization. Moreover, positively charged grooves on the surface of the dimer suggest a function in channeling of substrate from TS to DHFR active sites. These features provide possible approaches for the design of new drugs to overcome antifolate resistance.
authors.affiliation: Department of Biochemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand.
authors.forename: Jirundon
authors.initials: J
authors.lastname: Yuvaniyama
authors.forename: Penchit
authors.initials: P
authors.lastname: Chitnumsub
authors.forename: Sumalee
authors.initials: S
authors.lastname: Kamchonwongpaisan
authors.forename: Jarunee
authors.initials: J
authors.lastname: Vanichtanankul
authors.forename: Worachart
authors.initials: W
authors.lastname: Sirawaraporn
authors.forename: Paul
authors.initials: P
authors.lastname: Taylor
authors.forename: Malcolm D
authors.initials: MD
authors.lastname: Walkinshaw
authors.forename: Yongyuth
authors.initials: Y
authors.lastname: Yuthavong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D004351:Drug Resistance; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D010961:Plasmodium / Q000201:enzymology; D010963:Plasmodium falciparum / Q000201:enzymology; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry*; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors* / Q000737:chemistry*
chemical_list: D005493:Folic Acid Antagonists; D009097:Multienzyme Complexes; C056930:thymidylate synthase-dihydrofolate reductase; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase