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

Takeguchi, N.; Saitoh, T.; Morii, M.; Yoshikawa, K.; Terada, H.

Journal of Biological Chemistry 260(16): 9158-9161


ISSN/ISBN: 0021-9258
PMID: 4019467
Accession: 005479640

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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 Pi. Without Pi, the dyes did not induce current fluctuation at concentrations of < 30 .mu.M. 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. Apparently, the mechanism of the uncoupling of oxidation phosphorylation by dicationic cyanine dyes in mitochondria is different from that of cationic uncouplers such as tetrabutyl ammonium ion.