New insights of falcipain 2 structure from Plasmodium falciparum 3D7 strain

Structure-Based Optimization of Protease–Inhibitor Interactions to Enhance Specificity of Human Stefin-A against Falcipain-2 from the Plasmodium falciparum 3D7 Strain

“…Although macromolecular therapy comes with its own pool of drawbacks in probable proteolytic degradation of the administered inhibitor, immune noncompliance, and difficulty in cell or tissue penetration by the drug; their utility as scaffold proteins to derive more stability, 69 the conscious choice of a host protein as a template for immunogenic compliance and using different cargos like cell penetrating peptides or CPPs 70−72 to allow easier transport across cells, can help bypass them. The plausible utility of an allosteric domain, PEGylation, and an active-inactive conformational switch, pertaining to the FP2 structure, has already been put forward in our previous study, 19 and these can further steer protein-engineering methods in exploring FP2−STFA dynamics.…”

“…We compared the structure of FP2 in the FP2–STFA complex with that of the previously solved iodoacetamide inactivated-FP2 structure from the 3D7 variant from our lab (PDB ID: 7EI0) and found no gross difference in back-bone folding with a rmsd value of 1.196 Å for Cα atoms of 241 residues of FP2. However, some side chains have adopted different rotamer conformations due to the binding of STFA, as shown in Figure A,B.…”

“…These altered conformations are mainly pronounced in the R-domain, commensurating with our earlier observation that the R-domain is disordered and also mediates the binding of Hb effectively. 19…”

“…17,18 In our earlier work, we solved the crystal structure of FP2 from a drug-resistant 3D7 strain, which rendered insightful details in structure-based malarial chemotherapy, validating altered surface electrostatics and postulating a conformational active-inactive switch of its hemoglobinase activity. 19 Although there have been multiple combinatorial lead-target optimization approaches to earmarking FP2 using pharmacophores, like vinyl sulfones, halomethyl ketones, or aldehydes as warheads, the general strategy is to identify a specific inhibitor that blocks the catalytic site of its cognate prey strongly. 20,21 However, such small molecules target FP2 orthologs with identical catalytic mechanisms, reducing their specificity for the target protease and increasing off-target effects owing to their high sequence and structural similarity with major lysosomal cysteine cathepsins in the host.…”

“…About 60–80% of host Hb is cleaved using a panel of food vacuolar proteases to provide amino acids for the parasite’s growth, survival, and osmotic stability. − These proteases, based on knockout and inhibition studies, have long been considered as attractive drug targets among which a group of trophozoite-stage papain like cysteine proteases called falcipains, are regarded druggable, having retarded in vitro parasite growth and allowed accumulation of uncleaved Hb, through E-64 and leupeptin inhibition. , The troop of falcipains ruptures the infected erythrocyte membranes and allows host cell invasion and trafficking of proteins, resulting in a further breach of host immunity. , Although downplay of Hb hydrolysis due to FP2 gene disruption in P. falciparum was found to be phenotypically transient, FP2 is reportedly the highest expressed protease in the hemoprotozoan parasite and the best studied enzyme among falcipains, making it a potential malarial chemotherapeutic target. , In our earlier work, we solved the crystal structure of FP2 from a drug-resistant 3D7 strain, which rendered insightful details in structure-based malarial chemotherapy, validating altered surface electrostatics and postulating a conformational active-inactive switch of its hemoglobinase activity …”