Highly efficient ligands for dihydrofolate reductase from Cryptosporidium hominis and Toxoplasma gondii inspired by structural analysis.

Phylogenetic classification of protozoa based on the structure of the linker domain in the bifunctional enzyme, dihydrofolate reductase-thymidylate synthase.

We have determined the crystal structure of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from Cryptosporidium hominis, revealing a unique linker domain containing an 11-residue alpha-helix that has extensive interactions with the opposite DHFR-TS monomer of the homodimeric enzyme. Analysis of the structure of DHFR-TS from C. hominis and of previously solved structures of DHFR-TS from ...

In vitro generation of novel pyrimethamine resistance mutations in the Toxoplasma gondii dihydrofolate reductase.

Pyrimethamine is a potent inhibitor of dihydrofolate reductase and is widely used in the treatment of opportunistic infections caused by the protozoan parasite Toxoplasma gondii. In order to assess the potential role of dhfr sequence polymorphisms in drug treatment failures, we examined the dhfr-ts genes of representative isolates for T. gondii virulence types I, II, and III. These strains exhi...

The crystal structure of dihydrofolate reductase-thymidylate synthase from Cryptosporidium hominis reveals a novel architecture for the bifunctional enzyme.

Disruption of the crossover helix impairs dihydrofolate reductase activity in the bifunctional enzyme TS-DHFR from Cryptosporidium hominis.

In contrast with most species, including humans, which have monofunctional forms of the folate biosynthetic enzymes TS (thymidylate synthase) and DHFR (dihydrofolate reductase), several pathogenic protozoal parasites, including Cryptosporidium hominis, contain a bifunctional form of the enzymes on a single polypeptide chain having both catalytic activities. The crystal structure of the bifuncti...

In vitro effects of folate inhibitors on Toxoplasma gondii.

Three sulfonamides and four dihydrofolate reductase inhibitors were tested alone and in combination to determine their in vitro effects on two strains of Toxoplasma gondii grown in MRC5 fibroblast tissue culture. Toxoplasma growth was quantitated by an enzyme immunoassay performed directly on the fixed cultures, and linear regression models were used to quantify the relationship between the opt...