Carbonylcyanide p-trifluoro-methoxyphenylhydrazone-induced change of mitochondrial membrane structure revealed by lipid and protein spin labeling

Abstract

Structural information on the phenomena accompanying uncoupling of oxidative phosphorylation in mitochondria was obtained using lipid and protein spin labels. The event of partitioning, observed with a small lipid spin label, the 4,4-dimethyl-2,2-dipentyl-oxazolidine-3-oxide (6-N-11) has been studied. The ratio of polar/hydrophobic part of the third line of the spectra was decreased in the presence of the uncoupler carbonylcyanide- p-trifluoro-methoxyphenylhydrazone (FCCP), probably indicating a higher proportion of hydrophobic environment of the label. Protein spin labels have been employed to study mobilities and rate of reduction of the labels. A long-chain maleimide spin label, the 3-2-(2-maleimidoethoxy)ethylcarbamoyl-2,2,5,5-tetramethyl-l-pyrrolidinyloxyl, in the presence of carbonylcyanide- p-trifluoro-methoxyphenylhydrazone revealed decreases of mobility and of the rate of reduction. Large amplification of these effects was obtained with a short-chain maleimide spin label, the 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. With this spin label, the effect of the uncoupler could be traced down to a concentration of 0.05 μ m. It is concluded that both membrane lipid and protein are changed simultaneously in the uncoupling event.