Antimalarial target vulnerability of the putative Plasmodium falciparum methionine synthase.

Plasmodium falciparum possesses a cobalamin-dependent methionine synthase (MS). MS is putatively encoded by the PF3D7_1233700 gene, which is orthologous and syntenic in Plasmodium. However, its vulnerability as an antimalarial target has not been assessed. We edited the PF3D7_1233700 and PF3D7_0417200 (dihydrofolate reductase-thymidylate synthase, DHFR-TS) genes and obtained transgenic P. falciparum parasites expressing epitope-tagged target proteins under the control of the glmS ribozyme. Conditional loss-of-function mutants were obtained by treating transgenic parasites with glucosamine. DHFR-TS, but not MS mutants showed a significant proliferation defect over 96 h, suggesting that P. falciparum MS is not a vulnerable antimalarial target.