The Flocculating Cationic Polypetide from Moringa oleifera Seeds Damages Bacterial Cell Membranes by Causing Membrane Fusion

Open Access
Author:
Shebek, Kevin Michael
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Manish Kumar, Thesis Supervisor
  • Darrell Velegol, Honors Advisor
Keywords:
  • Antimicrobial
  • Polypeptide
  • Moringa
  • Oleifera
  • cryoEM
Abstract:
A cationic protein isolated from the seeds of the Moringa oleifera tree has been extensively studied for use in water treatment in developing countries and has been proposed for use in antimicrobial and therapeutic applications. However, the molecular basis for the antimicrobial action of this peptide, Moringa oleifera cationic protein (MOCP), has not been previously elucidated. We demonstrate here that a dominant mechanism of MOCP antimicrobial activity is derived from its fusogenic nature. We used a combination of cryogenic electron microscopy (cryoEM) and Förster resonance energy transfer (FRET) to observe and study the kinetics of fusion of membranes in liposomes representing model microbial cells. The cryoEM experiments showed vesicle fusion between the liposomes and FRET yielded results also indicative of membrane fusion. We also conducted cryoEM experiments on E. coli cells where MOCP was seen to fuse the inner and outer membranes. Coarse grained molecular dynamics simulations of membrane vesicles with MOCP molecules were used to elucidate steps in peptide adsorption, stalk formation and fusion between membranes.