scholarly journals The relationship between the rate of respiration and the protonmotive force. The role of proton conductivity

1984 ◽  
Vol 219 (2) ◽  
pp. 401-404 ◽  
Author(s):  
P S O'Shea ◽  
J B Chappell
Keyword(s):  
Proton Conductivity ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Protonmotive Force ◽  
Specific Rate ◽  
Chemiosmotic Hypothesis ◽  
The Relationship

It is shown by titrating a suspension of rat liver mitochondria with either ADP or an uncoupler that a specific rate of respiration may not have a unique associated value of the protonmotive force. Alternatively, a specific protonmotive force may not be associated with a unique rate of respiration. It seems that the rate of respiration and the protonmotive force are more sensitive to the agents used for the titrations than to each other. Such observations are not easily explained by the chemiosmotic hypothesis. It is, however, possible provided that the proton conductivities, i.e. the rates of dissipation of the protonmotive force, are considered to be different for each of the agents used to titrate the rate of respiration at the same protonmotive force, or vice versa.

Synthesis of Adenosine Triphosphate by a Protonmotive Force in Rat Liver Mitochondria

Nature ◽  
1966 ◽  
Vol 212 (5059) ◽  
pp. 257-258 ◽  
Author(s):  
R. A. REID ◽  
JENNIFER MOYLE ◽  
PETER MITCHELL
Keyword(s):  
Adenosine Triphosphate ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Protonmotive Force

scholarly journals Oxygen-pulse curves in rat liver mitochondrial suspensions. Some observations and deductions

1979 ◽  
Vol 180 (1) ◽  
pp. 161-174 ◽  
Author(s):  
G P Archbold ◽  
C L Farrington ◽  
S A Lappin ◽  
A M McKay ◽  
F H Malpress
Keyword(s):  
Rat Liver ◽  
Atp Synthesis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Protonmotive Force ◽  
Mitochondrial Inner Membrane ◽  
Fixed Charges ◽  
Charge Concentration ◽  
C 50 ◽  
Proton Movement

1. The inference, implicit in the chemiosmotic hypothesis, that protons move into the bulk phase during ATP synthesis was investigated. 2. Incubation of rat liver mitochondria in the presence of the cation exchanger CM-Sephadex C-50 caused alkalinization in the medium, though total ATP synthesis remained unchanged. The addition of N-ethylmaleimide prevented the alkalinization, but there was still no indication of protons passing into the medium. The expected proton movement [Mitchell & Moyle (1967) Biochem. J. 105, 1147–1162] was readily detected when as an equivalent acid pulse. 3. Analysis of delta H+ decay curves after O2 pulses (3 micrograms-atoms of O/g of protein) indicated the presence of fast and slow components of decay, with first-order rate constants (k) of 0.24s-1 and 0.032s-1. The fast decay was finite and was eliminated in the presence of N-ethylmaleimide. 4. These observations are interpreted as evidence for the development of unmasking of fixed charges on the outer surface of the mitochondrial inner membrane during energization and for the existence of proton-retentive electrical fields (rho-zones) on this surface. The charge concentration is calculated as about 1 charge/10nm2. 5. A cycle of changes in a single fixed-charge molecule is proposed which mediates both Ca2+ uptake and the first step in the utilization of the rho-zone protonmotive force, delta p rho.

Role of calcium and superoxide dismutase in sensitizing mitochondria to peroxynitrite-induced permeability transition

2004 ◽  
Vol 286 (1) ◽  
pp. H39-H46 ◽  
Author(s):  
Paul S. Brookes ◽  
Victor M. Darley-Usmar
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Rat Liver ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Ptp Opening ◽  
Isolated Rat

The mitochondrial permeability transition pore (PTP) is a membrane protein complex assembled and opened in response to Ca2+ and oxidants such as peroxynitrite (ONOO–). Opening the PTP is mechanistically linked to the release of cytochrome c, which participates in downstream apoptotic signaling. However, the molecular basis of the synergistic interactions between oxidants and Ca2+ in promoting the PTP are poorly understood and are addressed in the present study. In isolated rat liver mitochondria, it was found that the timing of the exposure of the isolated rat liver mitochondria to Ca2+ was a critical factor in determining the impact of ONOO– on PTP. Specifically, addition of Ca2+ alone, or ONOO– and then Ca2+, elicited similar low levels of PTP opening, whereas ONOO– alone was ineffective. In contrast, addition of Ca2+ and then ONOO– induced extensive PTP opening and cytochrome c release. Interestingly, Cu/Zn-superoxide dismutase enhanced pore opening through a mechanism independent of its catalytic activity. These data are consistent with a model in which Ca2+ reveals a molecular target that is now reactive with ONOO–. As a test of this hypothesis, tyrosine nitration was determined in mitochondria exposed to ONOO– alone or to Ca2+ and then ONOO–, and mitochondrial membrane proteins were analyzed using proteomics. These studies suggest protein targets revealed by Ca2+ include dehydrogenases and CoA-containing enzymes. These data are discussed in the context of the role of mitochondria, Ca2+, and ONOO– in apoptotic signaling.

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