Brand 1976 Proc Natl Acad Sci USA

Brand MD, Reynafarje B, Lehninger AL (1976) Stoichiometric relationship between energy-dependent proton ejection and electron transport in mitochondria. Proc Natl Acad Sci U S A 73: 437-441

» PMID:1061146 Open Access

Brand MD, Reynafarje B, Lehninger AL (1976) Proc Natl Acad Sci U S A

Abstract: The number of protons ejected during electron transport per pair of electrons per energy-conserving site (the H⁺/site ratio) was measured in rat liver mitochondria by three different methods under conditions in which transmembrane movements of endogenous phosphate were minized or eliminated.

1. In the Ca²⁺ pulse method, between 3.5 and 4.0 molecules of 3-hydroxybutyrate and 1.75 to 2.0 Ca²⁺ ions were accumulated per 2 e^- per site during Ca²⁺ induced electron transport in the presence of rotenone, when measured under conditions in which movements of endogenous phosphate were negligible. Since entry of 3-hydroxybutyrate requires its protonation to the free acid these data correspond to an H⁺/site ratio of 3.5-4.0
2. In the oxygen pulse method addition of known amounts of oxygen to anaerobic mitochondria in the presence of substrate yielded H⁺/site ratios of 3.0 when phosphate transport was eliminated by addition of N-ethylmaleimide or by anaerobic washing to remove endogenous phosphate. In the absence of such measures the observed H⁺/site ratio was 2.0.
3. In the reductant pulse method measurement of the initial steady rates of H⁺ ejection and oxygen consumption by mitochondria in an aerobic medium after addition of substrate gave H⁺/site near 4.0 in the presence of N-ethylmaleimide; in the absence of the inhibitor the observed ratio was only 2.0.

Abstract Continued in Free Text • Keywords: energy-dependent proton ejection, electron transport

Labels: MiParea: Respiration 

Organism: Rat  Tissue;cell: Liver  Preparation: Isolated Mitochondria"Isolated Mitochondria" is not in the list (Intact organism, Intact organ, Permeabilized cells, Permeabilized tissue, Homogenate, Isolated mitochondria, SMP, Chloroplasts, Enzyme, Oxidase;biochemical oxidation, ...) of allowed values for the "Preparation" property. 

Regulation: Coupling efficiency; uncoupling"Coupling efficiency; uncoupling" is not in the list (Aerobic glycolysis, ADP, ATP, ATP production, AMP, Calcium, Coupling efficiency;uncoupling, Cyt c, Flux control, Inhibitor, ...) of allowed values for the "Respiration and regulation" property., Ion&substrate transport"Ion&substrate transport" is not in the list (Aerobic glycolysis, ADP, ATP, ATP production, AMP, Calcium, Coupling efficiency;uncoupling, Cyt c, Flux control, Inhibitor, ...) of allowed values for the "Respiration and regulation" property., pH 

Made history 

Abstract Cont.

These and other experiments reported indicate that the values of 2.0 earlier obtained for the H⁺/site ratio by Mitchell and Moyle [Biochem J. (1967) 105, 1147-1162] and others were underestimates due to the unrecognized masking of H⁺ ejection by movements of endogenous phosphate. The results presented here show that the H⁺/site ratio of mitochondrial electron transport is at least 3.0 and may be as high as 4.0.