Figure 1.
Discovering the lead compounds against L.
mexicana CPB2.8∆CTE.
Set up of the screening library and filtering steps during hit enrichment. Four confirmed leads were finally identified by the hit enrichment workflow: one of the warhead-type semicarbazone, two of the warhead-type thiosemicarbazone and one of the warhead-type triazine nitrile.
Figure 2.
Confirmed lead structures inhibiting CPB2.8∆CTE of L.
mexicana.
Two thiosemicarbazones (CP247129 and CP247128), one nitrile (CP241026) and one semicarbazone (CP229988).
Figure 3.
Schematic representation of the covalent binding of warheads for the covalent docking process.
Atoms that form the covalent bond are labeled P in the protein and L in the ligand. Covalent bonds between P and L are indicated with dashed lines. (a-d) Reaction between thiosemicarbazone[30], nitrile[31] and semicarbazone warhead of the ligand and the catalytic cysteine residue of the protein.
Figure 4.
Covalent docking solutions of thiosemicarbazone-, nitrile- and semicarbazone-based inhibitors in the active site of the L.
mexicana CPB2.8∆CTE homology model (A, C, E, G) and the X-ray structure of BtCatB (B, D, F, H).
The transparent solvent accessible surface of the active sites is colored by lipophilic potential. The color ramp ranges from brown (highest lipophilic area of the surface) to blue (highest hydrophilic area of the surface). The relevant cysteine residue has been excluded from surface generation for visibility reasons of the covalent bond between the enzyme and the inhibitor molecule. Relevant amino acids of the active sites and the corresponding inhibitors are depicted in capped-stick representation and colored by atom type. The yellow arrow marks the covalent bond between the catalytic cysteine and the inhibitor. A: CP247129 covalently docked into the active site of CPB2.8∆CTE, B: CP247129 covalently docked into the active site of BtCatB, C: CP247128 covalently docked into the active site of CPB2.8∆CTE, D: CP247128 covalently docked into the active site of BtCatB, E: CP241026 covalently docked into the active site of CPB2.8∆CTE, F: CP241026 covalently docked into the active site of BtCatB, G: CP229988 covalently docked into the active site of CPB2.8∆CTE, H: CP229988 covalently docked into the active site of BtCatB.
Figure 5.
Semicarbazone scaffold and numbering of atoms.