Open AccessAmino acids in the dihydrofolate reductase-thymidylate synthase gene of Plasmodium falciparum involved in cycloguanil resistance differ from those involved in pyrimethamine resistance.
Author(s) -
Simon J. Foote,
Denise Galatis,
Alan F. Cowman
Publication year - 1990
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.87.8.3014
Subject(s) - dihydrofolate reductase , pyrimethamine , dihydropteroate synthase , plasmodium falciparum , biology , proguanil , antifolate , thymidylate synthase , serine , asparagine , biochemistry , enzyme , genetics , malaria , antimetabolite , fluorouracil , chemotherapy , immunology
Cycloguanil, the active metabolite of the antimalarial drug proguanil, is an inhibitor of dihydrofolate reductase as is another antimalarial, pyrimethamine. Its use has been limited by the rapid development of resistance by parasites around the world. We have determined the cycloguanil- and pyrimethamine-sensitivity status of 10 isolates of Plasmodium falciparum and have sequenced in all these isolates the dihydrofolate reductase (DHFR; 5,6,7,8-tetrahydrofolate: NADP+ oxidoreductase, EC 1.5.1.3) portion of the DHFR-thymidylate synthase (TS; 5,10-methylenetetrahydrofolate: dUMP C-methyltransferase, EC 2.1.1.45) gene. Instead of the known serine-to-asparagine change at position 108 that is important in pyrimethamine resistance, a serine-to-threonine change at the same position is found in cycloguanil-resistant isolates along with an alanine-to-valine change at position 16. We conclude that pyrimethamine and cycloguanil resistance most commonly involve alternative mutations at the same site. However, we also have identified a parasite with a unique set of changes that results in resistance to both drugs.