Abstract
Extracellular vesicles (EVs) are biogenic lipidic nanoparticles with a diameter of 30 ～ 200 nm that are secreted from almost all cells including bacterial cells. They have attracted an attention as important targets in not only biological but also medical science fields because they contain biomarkers and signaling molecules involved in diverse human diseases and bacterial pathogenesis. We have used curvature–sensing peptides to develop a simple and rapid method for in–situ vesicle detection in cultured media without EV–purification steps. The curvature–sensing peptides are now used as novel tools for marker–independent EV detection techniques. Currently, we investigated structural factors governing binding of curvature–sensing peptides to bacterial EVs covered with hydrophilic polysaccharide chains. The structurally flexible peptides, which underwent dynamic conformational changes from the random coil to α– helix, could bind to vesicles with similar binding affinities regardless of the membrane surface covered with hydrophilic polysaccharide chains or not. In contrast, structurally restricted peptides, which had less structural conversion, showed different binding affinities for vesicles depending on their surface condition. This is probably because curvature–sensing peptides must pass through the layer of hydrophilic polysaccharide chains prior to binding to the hydrophobic membrane surface. Therefore, we concluded that the structural flexibility of curvature–sensing peptides is a key factor for governing the highly sensitive detection of bacterial EVs.
