title: Interaction of pyrimethamine, cycloguanil, WR99210 and their analogues with Plasmodium falciparum dihydrofolate reductase: structural basis of antifolate resistance.
abstract: The nature of the interactions between Plasmodium falciparum dihydrofolate reductase (pfDHFR) and antimalarial antifolates, i.e., pyrimethamine (Pyr), cycloguanil (Cyc) and WR99210 including some of their analogues, was investigated by molecular modeling in conjunction with the determination of the inhibition constants (Ki). A three-dimensional structural model of pfDHFR was constructed using multiple sequence alignment and homology modeling procedures, followed by extensive molecular dynamics calculations. Mutations at amino acid residues 16 and 108 known to be associated with antifolate resistance were introduced into the structure, and the interactions of the inhibitors with the enzymes were assessed by docking and molecular dynamics for both wild-type and mutant DHFRs. The Ki values of a number of analogues tested support the validity of the model. A 'steric constraint' hypothesis is proposed to explain the structural basis of the antifolate resistance.
authors.affiliation: Dipartimento di Scienze Farmaceutiche, Universita di Modena e Reggio Emilia, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Rastelli
authors.forename: W
authors.initials: W
authors.lastname: Sirawaraporn
authors.forename: P
authors.initials: P
authors.lastname: Sompornpisut
authors.forename: T
authors.initials: T
authors.lastname: Vilaivan
authors.forename: S
authors.initials: S
authors.lastname: Kamchonwongpaisan
authors.forename: R
authors.initials: R
authors.lastname: Quarrell
authors.forename: G
authors.initials: G
authors.lastname: Lowe
authors.forename: Y
authors.initials: Y
authors.lastname: Thebtaranonth
authors.forename: Y
authors.initials: Y
authors.lastname: Yuthavong
mesh_terms: D000595:Amino Acid Sequence; D004351:Drug Resistance; D005493:Folic Acid Antagonists / Q000737:chemistry / Q000494:pharmacology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D002727:Proguanil; D011739:Pyrimethamine / Q000737:chemistry / Q000494:pharmacology*; D017386:Sequence Homology, Amino Acid; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000187:drug effects*; D014227:Triazines / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D005493:Folic Acid Antagonists; D014227:Triazines; C026009:cycloguanil; C006201:BRL 6231; D013762:Tetrahydrofolate Dehydrogenase; D002727:Proguanil; D011739:Pyrimethamine