Exploring Heme and Hemoglobin Binding Regions of Plasmodium Heme Detoxification Protein for New Antimalarial Discovery

Abstract

Hemoglobin degradation/hemozoin formation, essential steps in the Plasmodium life cycle, are targets of existing antimalarials. The pathway still offers vast possibilities to be explored for new antimalarial discoveries. Here, we characterize heme detoxification protein, PfHDP, a major protein involved in hemozoin formation, as a novel drug target. Using in silico and biochemical approaches, we identified two heme binding sites and a hemoglobin binding site in PfHDP. Treatment of Plasmodium falciparum 3D7 parasites with peptide corresponding to the hemoglobin binding domain in PfHDP resulted in food vacuole abnormalities similar to that seen with a cysteine protease inhibitor, E-64 (I-1). Screening of compounds that bound the modeled PfHDP structure in the heme/hemoglobin-binding pockets from Maybridge Screening Collection identified a compound, ML-2, that inhibited parasite growth in a dose-dependent manner, thus paving the way for testing its potential as a new drug candidate. These results provide functional insights into the role of PfHDP in Hz formation and further suggest that PfHDP could be an important drug target to combat malaria.

Antiplasmodial Activity and In Vivo Bio-Distribution of Chloroquine Molecules Released with a 4-(4-Ethynylphenyl)-Triazole Moiety from Organometallo-Cobalamins

“…Chloroquine (CQ) exerts its antimalarial function by inhibiting hemozoin formation during the critical ferriheme detoxification process of the Plasmodium parasite [35,36,37,38,39]. The molecule acts either by: (a) directly complexing monomeric PPIX preventing its incorporation into the growing hemozoin crystals [36,40,41,42], (b) capping the hemozoin crystal [43,44], (c) binding to PPIX via π–π interactions between the its aromatic ring and the porphyrin ring [45,46], (d) shifting the haematin/μ-oxo PPIX dimer equilibrium [40], or (e) docking onto the fastest growing crystal face [47].…”

Comparative Analysis of Erythrocyte Proteomes of Water Buffalo, Dairy Cattle, and Beef Cattle by Shotgun LC-MS/MS

“…The number of proteins in oxygen binding (GO:0019825) in water buffalo is far higher than in beef cattle and dairy cattle, which increases the significance of deep investigation of these two proteins. Hemoglobin is vital to hemoprotozoan survival inside the RBC and, to date, it is regarded as the main energy source for most of the hemoprotozoan (35). Moreover, hemoglobin is covalently modified in order to inhibit the intake of amino acids by plasmodium but does not affect the normal functions (36).…”

Drugs in Development for Malaria

“…Another target that has garnered a lot of interest is Na + -ATPase 4, the site of action of the potent cipargamin and SJ557733, both in clinical development, and of 21A092, a pyrazoleamide in the discovery phase [ 98 ]. Pathways involved in haem detoxification are also under study [ 99 ]. Work continues on developing parasite-selective inhibitors of phenylalanyl-tRNA synthetase, histone deacetylase, hypoxanthine–guanine–(xanthine) phosphoribosyltransferase and N-myristoyltransferase [ 100 – 103 ].…”