Mitchell 1969 Eur J Biochem
| Mitchell P, Moyle J (1969) Estimation of membrane potential and pH difference across the cristae membrane of rat liver mitochondria. Eur J Biochem 7: 471-484. |
Mitchell P, Moyle J (1969) Eur J Biochem
Abstract: The cristae membrane or M phase of resting or respiring rat liver mitochondria becomes relatively permeable to K+ ions in presence of valinomycin. The equilibrium distribution of K+ ions across the membrane can therefore be used to estimate the membrane potential ΔΨ provided that precautions are taken to minimise swelling of the valinomycin-treated mitochondria. The pH difference ΔpH across the M phase of anaerobic mitochondria has been estimated from the buffering powers of the inner and outer phases and from the change of pH observed on lysing the mitochondria with Triton X-100. When the anaerobic mitochondria (State 5), in presence of β-hydroxybutyrate, are brought to a state of steady respiration either in absence (State 4) or in presence (State 3) of phosphate acceptor, the changes of pH and of pK of the medium recorded with H+ ion-sensitive and K+ ion-sensitive electrodes can be used to estimate the changes of ΔΨ and ΔpH across the M phase. The absolute values of ΔΨ and ΔpH have been estimated from the values determined in State 5 and the change of these values in the transition from State 5 to States 4 and 3.
Continued in Free Text • Keywords: membrane potential, pH difference, cristae membrane, valinomycin, K+ ions
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 Continued
The total protonmotive force Δp =ΔΨ– 59 ΔpH across the M phase of the mitochondria oxidising β-hydroxybutyrate in State 4 at 25° in a 250 mM sucrose medium near pH 7 is estimated to be about 230 mV, of which the major component is ΔΨ when the effect of translocation of K+ ions across the M phase is minimised. Under conditions permitting accumulation of a relatively large quantity of cation (State 6), Δp is not significantly different from that in State 4, but the major component is −ZΔpH.
The effects of changing Δp in mitochondrial suspensions in State 4 with uncoupling agent and with pulses of acid, alkali, calcium salt and ADP have been found to be in accord with the chemiosmotic hypothesis. In particular Δp in State 3 (ADP and Pi present) is estimated to be about 30 mV less than in State 4.
