ISSN:
1573-6881
Keywords:
Oxidative phosphorylation
;
energy communication
;
affinity change
;
kinetic modalities
;
membrane potential
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract This article reviews the current status of information regarding the role of energy in the process of oxidative phosphorylation by mitochondria. The available data suggest that in submitochondrial particles (SMP) energy is utilized for the binding of ADP and Pi and for the release of ATP bound at the catalytic sites of F1-ATPase. The process of ATP synthesis on the surface of F1 from F1-bound ADP and Pi appears to be associated with negligible free energy change. The rate of energy production by the respiratory chain modulates the kinetics of ATP synthesis between a lowK m (for ADP and Pi)-lowV max mode and a highK m -highV max mode. TheK m extremes for ADP are 2–3 µM and 120–150 µM, andV max for ATP synthesis at high rates of energy production by bovine-heart SMP is about 440 s−1 (mole F1)−1 at 30°C, which corresponds to 11 µmol ATP (min · mg of protein)−1. The interaction of dicyclohexylcarbodiimide (DCCD) or oligomycin at the proteolipid (subunitc) of the membrane sector (F0) of the ATP synthase complex alters the mode of ATP binding at the catalytic sites of F1, probably to one of lower affinity. It has been suggested that protonic energy might be conveyed to the catalytic sites of F1 in an analogous manner, i.e., via conformation changes in the ATP synthase complex initiated by proton-induced alterations in the structure of the DCCD-binding proteolipid. Finally, the relationship between the steady-state membrane potential (Δψ) and the rates of electron transfer and ATP synthesis has been discussed. It has been shown, in agreement with the delocalized chemiosmotic mechanism, that under appropriate conditions Δψ is exquisitely sensitive to changes in the rates of energy production and consumption.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00762205
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