Thermodynamic Evaluation of Ligand Binding in the Plant-like Phosphoethanolamine Methyltransferases of the Parasitic Nematode Haemonchus contortus

Abstract

Background: Phosphoethanolamine methyltransferases (PMT) are required for growth and development of nematodes. Result: Biochemical studies of two PMT from a parasitic nematode reveal key similarities and differences. Conclusion: Although the nematode PMT are conserved, the domains that catalyze specific reactions may undergo different conformational changes upon ligand binding. Significance: Because the PMT are not found in mammals, these proteins are potential antiparasitic targets for human and veterinary medicine.

Conformational changes in the di-domain structure of Arabidopsis phosphoethanolamine methyltransferase leads to active-site formation

“…S2, A-C, insets) and eluted from the size-exclusion column as a monomer (ϳ50 -60 kDa) (supplemental Fig. S2D), which was similar to the spinach and nematode enzymes (8,10,11,17,20).…”

“…In contrast to the simplification of PMT architecture observed in the apicomplexans, the evolutionary path to the two mono-functional di-domain proteins found in nematodes appears to have involved gene duplication and structural alterations that yielded vestigial non-functional domains (Fig. 8) (10,11,20). Although the domain organization of each type of PMT varies, the overall structure within each domain is highly conserved across a range of evolutionarily distant and diverse organisms.…”

Structure and Reaction Mechanism of Phosphoethanolamine Methyltransferase from the Malaria Parasite Plasmodium falciparum

“…1A) provides Plasmodium with a novel and essential metabolic route for membrane biogenesis that is not found in mammals (7)(8)(9)(10). In addition, this pathway is also required for growth and development in C. elegans (11)(12)(13)(14)19). Given the biological function of the PMT in Plasmodium and nematodes and that these enzymes are not found in mammals, the PMT are potential targets for the development of antiparasitic therapeutics (10,13,14,17).…”

“…All data were fit to the Michaelis-Menten equation in SigmaPlot. Calorimetric analysis of AdoCys and pCho binding to PfPMT was performed, and data were analyzed as described previously for the nematode PMT (19).…”

An Alternative Mechanism for the Methylation of Phosphoethanolamine Catalyzed by Plasmodium falciparum Phosphoethanolamine Methyltransferase*

“…Steady-state kinetic analysis of wild-type and mutant PfPMT was performed as described previously (8,9,18). Isothermal titration calorimetry (ITC) was used to monitor AdoHcy and pCho binding to wild-type and mutant PfPMT, as described previously (10,18).…”