J. Biol. Chem., Vol. 260, Issue 16, 9158-9161, Aug, 1985
Formation of a leakage-type ion pathway in lipid bilayer membranes by divalent cationic cyanine dyes in cooperation with inorganic phosphate. Role of the cyanine dye in uncoupling of oxidative phosphorylation
N Takeguchi, T Saitoh, M Morii, K Yoshikawa and H Terada
Divalent cationic cyanine dyes, such as 2,2'-[3-[2-(3-butyl-4-methyl-2-
thiazoline-2-ylidene)-ethylidene] propenylene]bis[3-butyl-4-
methylthiazolinium iodide] and platonin induced large membrane current
fluctuation when an electrical potential difference was applied across a
planar phosphatidylserine bilayer membrane in medium containing inorganic
phosphate (Pi). Without Pi, the dyes did not induce current fluctuation at
concentrations of less than 30 microM. Noise analysis of current
fluctuation indicated formation of a pathway for ion leakage. From
measurements of the interfacial tension between oil and aqueous phases, and
of water permeability across liposomal membranes, Pi was concluded to relax
the phospholipid bilayer structure, resulting in great reduction in the
concentration of the cyanine dye necessary for induction of the
leakage-type pathway. In the presence of Pi, cationic ions such as
tetrabutyl ammonium and tetraphenyl phosphonium did not induce the
leakage-type pathway, although they had electrophoretic effects at high
concentrations. These facts suggest that the mechanism of the uncoupling of
oxidative phosphorylation by dicationic cyanine dyes in mitochondria is
different from that of cationic uncouplers such as tetrabutyl ammonium ion.
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