Effect of oxidative phosphorylation inhibitors and uncoupling agents on cAMP activity

Uncouplers of oxidative phosphorylation increased the speed of substrate oxidation and ATP hydrolysis and raised cAMP induced neuron membrane current. Different inhibitors decreased it. Both effects support the hypothesis that a signal of intracellular injected cAMP spreads to the neuron membrane as a mechanical signal. This signal propagated to the membrane along microtubules which according to this hypothesis serve as a sound generator with metabolic heat pumping.     

Prostaglandin production by methylcholanthrene-transformed mouse BALB/3T3: Effect of oxidative phosphorylation inhibitors

Oligomycin, antimycin, and 2,4-dinitrophenol, compounds that are known to inhibit oxidative phosphorylation by different mechanisms, inhibit the production of prostaglandins by serum-stimulated MC5-5 cells. The prostaglandin production that is stimulated by thrombin and bradykinin is inhibited by 2,4-dinitrophenol. Prostaglandin synthesis by MC5-5 cells from exogenously-supplied arachidonic acid, however, is not affected by 2,4-dinitrophenol. Antimycin and 2,4-dinitrophenol also inhibit the serum-stimulated release of arachidonic acid from the cellular lipids, suggesting that it is the expression of phospholipase activity, a prerequisite for synthesis of prostaglandins by MC5-5 cells, that is dependent on oxidative phosphorylation.     

Supercomplex organization of the oxidative phosphorylation enzymes in yeast mitochondria

Accumulating evidence indicates that the enzymes involved in mitochondrial oxidative phosphorylation (OXPHOS) are co-assembled into higher-ordered supercomplexes within the mitochondrial inner membrane. This review will focus largely on the OXPHOS supercomplexes of the yeast Saccharomyces cerevisiae. The recent evidence to indicate that diversity in the populations of the cytochrome bc (1)-COX supercomplexes exist shall be outlined. In addition, the existence of dimeric/oligomeric F(1)F(o)-ATP synthase complexes and their proposed role in establishment of the cristae architecture of the inner mitochondrial membrane shall also be discussed.     

Effect of parthenin on mitochondrial oxidative phosphorylation

The sesquiterpene lactone, 'parthenin' the toxic principle of the allergenic weed Parthenium hysterophorus, inhibited 'state 3' respiration and stimulated 'state 4' respiration in rat liver and kidney mitochondria as well as ATPase activity in the presence of Mg2+ ions. These properties indicate that the toxic action of parthenin may be related to its interference with oxidative phosphorylation.     

Effect of photosynthetic inhibitors and uncouplers of oxidative phosphorylation on nitrate and nitrite reduction in barley leaves

The effects of several photosynthetic inhibitors and uncouplers of oxidative phosphorylation on NO₃⁻ and NO₂⁻ assimilation were studied using detached barley (Hordeum vulgare L. cv Numar) leaves in which only endogenous NO₃⁻ or NO₂⁻ were available for reduction. Uncouplers of oxidative phosphorylation greatly increased NO₃⁻ reduction in both light and darkness, while photosynthetic inhibitors did not.

The NO₂⁻ concentration in the control leaves was very low in both light and darkness; 98% or more of the NO₂⁻ formed from NO₃⁻ was further assimilated in control leaves. More NO₂⁻ accumulated in the leaves in light and darkness in the presence of photosynthetic inhibitors. Of this NO₂⁻, 94% or more was further assimilated. It appears that metabolites, either external or internal to the chloroplast, capable of reducing NADP (which, in turn, could reduce ferredoxin via NADP reductase) might support NO₂⁻ reduction in darkness and light when photosynthetic electron flow is inhibited by photosynthetic inhibitors.

Nitrite assimilation was much more sensitive to uncouplers in darkness than in light: in darkness, 74% or more of NO₂⁻ formed from NO₃⁻ was further assimilated, whereas in light, 95% or more of the NO₂⁻ was further assimilated.