The Flocculating Cationic Polypetide from <i>Moringa oleifera</i> Seeds Damages Bacterial Cell Membranes
by Causing Membrane Fusion
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Abstract
A cationic protein isolated from
the seeds of the <i>Moringa
oleifera</i> 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, <i>Moringa
oleifera</i> cationic protein (MOCP), has not been previously
elucidated. We demonstrate here that a dominant mechanism of MOCP
antimicrobial activity is membrane fusion. We used a combination of
cryogenic electron microscopy (cryo-EM) and fluorescence assays to
observe and study the kinetics of fusion of membranes in liposomes
representing model microbial cells. We also conducted cryo-EM experiments
on <i>E. coli</i> 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