The Influence of Membrane Lipids in Staphylococcusaureus Gamma-Hemolysins Pore Formation

The Influence of Membrane Lipids in Staphylococcusaureus Gamma-Hemolysins Pore Formation The natural target of Staphylococcus aureus bicomponent γ-hemolysins are leucocyte cell membranes. Because a proteinaceous receptor has not been found yet, we checked for the importance of the different membrane lipid compositions by measuring the activity of the toxin on several pure lipid model membranes. We investigated the effect of membrane thickness, fluidity, and presence of nonbilayer lipids and found that the toxin pore-forming ability increased in the presence of phosphocholines with short saturated acyl chains or with unsaturated chains even though not short. An increase of activity was also evident in the presence of cone-shaped lipids like phosphatidylethanolamine or diphytanoylphosphatidylcholine, whereas cylindrical lipids, like sphingomyelin, did not favor the activity. All these results suggest that γ-hemolysins could bind to the bilayer only if the phosphatidylcholine (PC) head is freely accessible. This condition is satisfied by the concurrent presence of cholesterol and certain lipids, as highlighted by the so-called umbrella model (J. Huang and G. W. Feigenson, Biophys J 76:2142–2157, 1999). According to this model, cholesterol could help to a better exposition of PC head groups only if acyl chains are short or unsaturated. In fact, phosphatidylcholines with more than 13 carbon atoms acyl chains can cover cholesterol molecules; in this way, PC head groups pack tightly, rendering them inaccessible to the toxin, which thus shows a reduced pore-forming ability. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

The Influence of Membrane Lipids in Staphylococcusaureus Gamma-Hemolysins Pore Formation

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Publisher
Springer-Verlag
Copyright
Copyright © 2008 by Springer Science+Business Media, LLC
Subject
Life Sciences; Human Physiology ; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-008-9140-6
Publisher site
See Article on Publisher Site

Abstract

The natural target of Staphylococcus aureus bicomponent γ-hemolysins are leucocyte cell membranes. Because a proteinaceous receptor has not been found yet, we checked for the importance of the different membrane lipid compositions by measuring the activity of the toxin on several pure lipid model membranes. We investigated the effect of membrane thickness, fluidity, and presence of nonbilayer lipids and found that the toxin pore-forming ability increased in the presence of phosphocholines with short saturated acyl chains or with unsaturated chains even though not short. An increase of activity was also evident in the presence of cone-shaped lipids like phosphatidylethanolamine or diphytanoylphosphatidylcholine, whereas cylindrical lipids, like sphingomyelin, did not favor the activity. All these results suggest that γ-hemolysins could bind to the bilayer only if the phosphatidylcholine (PC) head is freely accessible. This condition is satisfied by the concurrent presence of cholesterol and certain lipids, as highlighted by the so-called umbrella model (J. Huang and G. W. Feigenson, Biophys J 76:2142–2157, 1999). According to this model, cholesterol could help to a better exposition of PC head groups only if acyl chains are short or unsaturated. In fact, phosphatidylcholines with more than 13 carbon atoms acyl chains can cover cholesterol molecules; in this way, PC head groups pack tightly, rendering them inaccessible to the toxin, which thus shows a reduced pore-forming ability.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Dec 9, 2008

References

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