Proton flux induced by free fatty acids across phospholipid bilayers: new evidences based on short-circuit measurements in planar lipid membranes.
Free fatty acids (FFA) are important mediators of proton transport across membranes. However, information concerning the influence of the structural features of both FFA and the membrane environment on the proton translocation mechanisms across phospholipid membranes is relatively scant. The effects of FFA chain length, unsaturation and membrane composition on proton transport have been addressed in this study by means of electrical measurements in planar lipid bilayers. Proton conductance (GH+) was calculated from open-circuit voltage and short-circuit current density measurements. We found that cis-unsaturated FFA caused a more pronounced effect on proton transport as compared to saturated and trans-unsaturated FFA. Cholesterol and cardiolipin decreased membrane leak conductance. Cardiolipin also decreased proton conductance. These effects indicate a dual modulation of protein-independent proton transport by FFA: through a flip-flop mechanism and by modifying a proton diffusional pathway. Moreover the membrane phospholipid composition was shown to importantly affect both processes.
Arcisio-Miranda
Manoel
M
Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes, 1580 Sala 101A, São Paulo 05508-900, Brazil. manoelarcisio@yahoo.com.br
Abdulkader
Fernando
F
Brunaldi
Kellen
K
Curi
Rui
R
Procopio
Joaquim
J
D005230:Fatty Acids, Nonesterified / Q000737:chemistry*; D008051:Lipid Bilayers; D010743:Phospholipids / Q000737:chemistry*; D011522:Protons
D005230:Fatty Acids, Nonesterified; D008051:Lipid Bilayers; D010743:Phospholipids; D011522:Protons