PEG400 regulates Falcipain 2 activity through an allosteric mechanism.

Area of Science:

• Biochemistry
• Parasitology
• Drug Discovery

Background:

• Malarial parasite Plasmodium falciparum relies on proteolytic enzymes to cleave host hemoglobin.
• Falcipain-2 (FP2), a cysteine protease, is crucial for parasite survival and a potential drug target.
• Structural similarities between FP2 and human cathepsins complicate selective inhibition.

Purpose of the Study:

• To investigate the regulatory role of polyethylene glycol 400 (PEG400) on Falcipain-2 (FP2) activity.
• To characterize the interaction of PEG400 with FP2 and its effect on hemoglobin degradation.
• To explore the potential for selective inhibition of FP2.

Main Methods:

• Enzyme activity assays using peptide substrates and azo-casein.
• Fluorescence quenching and molecular docking studies to determine binding interactions.
• Computational analyses including in silico mutagenesis and molecular dynamics simulations.
• Normal mode analysis to study protein dynamics.

Main Results:

• PEG400 exhibits mixed-type inhibition of FP2 on small peptide substrates but enhances hemoglobin degradation.
• PEG400 binds to the catalytic cleft of FP2 and an allosteric pocket with low conservation in human cathepsins.
• PEG400 alters hemoglobin structure and dynamics, promoting proteolysis.
• PEG400 influences FP2 hinge-bending motion, enhancing FP2-hemoglobin interaction and subsequent proteolysis.

Conclusions:

• PEG400 demonstrates a novel dual regulatory mechanism on FP2 activity.
• The identified allosteric binding pocket offers potential for selective FP2 inhibition.
• Understanding this interaction provides new therapeutic strategies against malaria.