Effect of fatty acyl domain of phospholipids on the membrane-channel formation of Staphylococcus aureus alpha-toxin in liposome membrane.
By use of carboxyfluorescein-loaded multilamellar liposomes prepared from synthetic phosphatidylcholine (PC) or sphingomyelin and cholesterol in a molar ratio of 1:1, we studied whether or not fatty acyl domain of the phospholipids affects the membrane-damaging action (or channel formation) of Staphylococcus aureus alpha-toxin on the phospholipid-cholesterol membranes. Our data indicated: (1) that toxin-induced carboxyfluorescein-leakage from the liposomes composed of saturated fatty acyl residue-carrying PC and cholesterol was decreased with increasing chain length of the acyl residues between 12 and 18 carbon atoms, although toxin-binding to the liposomes was not significantly affected by the length of fatty acyl residue; (2) that unsaturated fatty acyl residue in PC or sphingomyelin molecule conferred higher sensitivity to alpha-toxin on the phospholipid-cholesterol liposomes, compared with saturated fatty acyl residues; and (3) that hexamerization of alpha-toxin, estimated by SDS-polyacrylamide gel electrophoresis, occurred more efficiently on the liposomes composed of PC with shorter fatty acyl chain or unsaturated fatty acyl chain. Thus, hydrophobic domain of the phospholipids influences membrane-channel formation of alpha-toxin in the phospholipid-cholesterol membrane, perhaps by modulating packing of phospholipid, cholesterol and the toxin in membrane.
Institute of Medical Science, University of Tokyo, Japan.
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Tomita
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Watanabe
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Yasuda
D004075:Diglycerides / Q000737:chemistry; D005452:Fluoresceins; D007473:Ion Channels; D008081:Liposomes / Q000737:chemistry*; D046911:Macromolecular Substances; D008566:Membranes / Q000737:chemistry; D010743:Phospholipids / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000201:enzymology; D010738:Type C Phospholipases / Q000737:chemistry*
D004075:Diglycerides; D005452:Fluoresceins; D007473:Ion Channels; D008081:Liposomes; D046911:Macromolecular Substances; D010743:Phospholipids; C024098:6-carboxyfluorescein; D010738:Type C Phospholipases