Surface localization of sites of reduction of nitroxide spin-labeled molecules in mitochrondria

Journal Article · Tue Feb 01 04:00:00 EST 1977 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.74.2.570· OSTI ID:7311012

Quintanilha, A T; Packer, L

The relative rates of reduction of several spin-labeled molecules that partition differently across the hydrophobic-interface of inner membranes from rat liver mitochondria were investigated. Spin labels localized either deep in the hydrophobic region or in the aqueous phase are only slowly reduced; however, a spin-labeled analogue of the cationic detergent cetyltrimethylammonium bromide that partitions at the interface is rapidly reduced by coupled electron transport. Chemical studies on the reduction and oxidation of the spin label show that loss of signal is due to reduction and not destruction of the label. No evidence was found for flip-flop of the label in submitochondrial preparations. Spin reduction of respiring mitochondria, mitoplasts, or inverted submitochondrial preparations is inhibited by rotenone but is relatively insensitive to antimycin A and KCN. Because the midpoint potentials of the spin labels were found to be similar to that of ubiquinone, it is concluded that reducing equivalents of mitochondrial electron transport from this region of the chain are channeled to either membrane interface.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 7311012
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 74:2; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ADDITIVES
AROMATICS
CELL CONSTITUENTS
CHEMICAL REACTIONS
DETERGENTS
ELECTRON TRANSFER
EMULSIFIERS
MEMBRANES
MITOCHONDRIA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANOIDS
QUINONES
REDUCTION
SURFACTANTS
WETTING AGENTS