H+/OH− permeation through lipid bilayers occurs at anomalously high rates and the determinants of proton flux through membranes are poorly understood. Since all life depends on proton gradients, it is important to develop a greater understanding of proton leak phenomena. We have used stopped-flow fluorimetry to probe the influence of two lipid raft components, chol (cholesterol) and SM (sphingomyelin), on H+/OH− and water permeability. Increasing the concentrations of both lipids in POPC (palmitoyl-2-oleoyl phosphatidylcholine) liposomes decreased water permeability in a concentration-dependent manner, an effect that correlated with increased lipid order. Surprisingly, proton flux was increased by increasing the concentration of chol and SM. The chol effect was complex with molar concentrations of 17.9, 33 and 45.7% giving 2.8-fold (P<0.01), 2.2-fold (P<0.001) and 5.1-fold (P<0.001) increases in H+/OH− permeability from a baseline of 2.4×10−2 cm/s. SM at 10 mole% effected a 2.8-fold increase (P<0.01), whereas 20 and 30 mole% enhanced permeability by 3.6-fold (P<0.05) and 4.1-fold respectively (P<0.05). Supplementing membranes containing chol with SM did not enhance H+/OH− permeability. Of interest was the finding that chol addition to soya-bean lipids decreased H+/OH− permeability, consistent with an earlier report [Ira and Krishnamoorthy (2001) J. Phys. Chem. B 105, 1484–1488]. We speculate that the presence of proton carriers in crude lipid extracts might contribute to this result. We conclude that (i) chol and SM specifically and independently increase rates of proton permeation in POPC bilayers, (ii) domains enriched in these lipids or domain interfaces may represent regions with high H+/OH− conductivity, (iii) H+/OH− fluxes are not governed by lipid order and (iv) chol can inhibit or promote H+/OH− permeability depending on the total lipid environment. Theories of proton permeation are discussed in the light of these results.
Skip Nav Destination
Follow us on Twitter @Biochem_Journal
Article navigation
September 2006
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
- PDF Icon PDF LinkEditorial Board
Research Article|
August 29 2006
Lipid raft components cholesterol and sphingomyelin increase H+/OH− permeability of phosphatidylcholine membranes Available to Purchase
Rebekah H. Gensure;
Rebekah H. Gensure
1Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A.
Search for other works by this author on:
Mark L. Zeidel;
Mark L. Zeidel
1Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A.
Search for other works by this author on:
Warren G. Hill
Warren G. Hill
1
1Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A.
1To whom correspondence should be addressed, at the present address: Beth Israel Deaconess Medical Center, 840 Memorial Drive, Cambridge, MA 02139, U.S.A. (email [email protected]).
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
October 03 2005
Revision Received:
April 25 2006
Accepted:
May 17 2006
Accepted Manuscript online:
May 17 2006
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2006
Biochem J (2006) 398 (3): 485–495.
Article history
Received:
October 03 2005
Revision Received:
April 25 2006
Accepted:
May 17 2006
Accepted Manuscript online:
May 17 2006
Citation
Rebekah H. Gensure, Mark L. Zeidel, Warren G. Hill; Lipid raft components cholesterol and sphingomyelin increase H+/OH− permeability of phosphatidylcholine membranes. Biochem J 15 September 2006; 398 (3): 485–495. doi: https://doi.org/10.1042/BJ20051620
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Biochemical Society Member Sign in
Sign InSign in via your Institution
Sign in via your InstitutionGet Access To This Article
Follow us on Twitter @Biochem_Journal
Open Access for all
We offer compliant routes for all authors from 2025. With library support, there will be no author nor reader charges in 5 journals. Check here |
![]() View past webinars > |