Monitoring of cholesterol oxidation in a lipid bilayer membrane using streptolysin O as a sensing and signal transduction element

[Display omitted] •A fluorometric method for monitoring chol oxidation in a lipid bilayer is described based on the pore forming ability of SLO.•The 3β-OH configuration of sterol in lipid bilayers is important for SLO to form a nanopore.•The P30min value decreased almost linearly with the mole fraction of 4-cholesten-3-one in immobilized liposomes.•The progress of enzymatic chol oxidation in liposomes was detected by utilizing the SLO. Streptolysin O (SLO), which recognizes sterols and forms nanopores in lipid membranes, is proposed as a sensing element for monitoring cholesterol oxidation in a lipid bilayer. The structural requirements of eight sterols for forming nanopores by SLO confirmed that a free 3-OH group in the β-configuration of sterols is required for recognition by SLO in a lipid bilayer. The extent of nanopore formation by SLO in lipid bilayers increased in the order of cholestanol