Fo F1 Research Articles

Adamantaniline Derivatives Target ATP5B to Inhibit Translation of Hypoxia Inducible Factor-1α.

Hypoxia inducible factor-1α (HIF-1α) plays a critical role in cellular adaptation to hypoxia and it is a potential therapeutic target for anti-cancer drugs. Applying high-throughput screening, here it is found that HI-101, a small molecule containing an adamantaniline moiety, effectively reduces HIF-1α protein expression. With the compound as a hit, a probe (HI-102) is developed for target identification by affinity-based protein profiling. The catalytic β subunit of mitochondrial FO F1 -ATP synthase, ATP5B, is identified as the binding protein of HI-derivatives. Mechanistically, HI-101 promotes the binding of HIF-1α mRNA to ATP5B, thus inhibiting HIF-1α translation and the following transcriptional activity. Further modifications of HI-101 lead to HI-104, a compound with good pharmacokinetic properties, exhibiting antitumor activity in MHCC97-L mice xenograft model, and HI-105, the most potent compound with an IC50 of 26nm. The findings provide a new strategy for further developing HIF-1α inhibitors by translational inhibition through ATP5B.

Ingo’s Register Treadmill

Ingo's Register Treadmill Ingo Titze (bio) VOICE RESEARCH AND TECHNOLOGY A register treadmill was proposed eight years ago as a diagnostic exercise for exposing involuntary register shifts in the D4 to A4 pitch range.1 The basic concept was to create pitch and vowel progressions that would elicit maximum crossings of harmonics with supraglottal resonances (formants) of the vocal tract. It is well known that sudden increases or decreases in harmonic amplitudes in proximity of a resonance can cause a timbral change that can be considered an acoustic registration.2 In particular, strengthening or weakening the second harmonic with the first formant can be responsible for such a register shift. A pentavowel sequence, combined with a pentatonic scale, was proposed such that source frequencies move in opposite direction to resonance frequencies. This produces multiple harmonic-resonance crossovers. This article is a follow-up to expand the treadmill to include a wider pitch range and sex differences in formant frequencies. While allophonic variations of formants F1 and F2 are large across individuals and languages, a smoothed penta-vowel sequence has been chosen here. Each sequence begins with a wide mouth shape and ends with a narrow mouth shape. Formant frequencies for females have been chosen to be 20 % higher than for males. All formant frequencies are listed below for two vowel sequences. High Vowel Sequence [æ] [ɛ] [e] [ɪ] [i] Male F1 670 550 420 350 280 Female F1 860 660 504 420 320 Male F2 1800 1900 2000 2200 2300 Female F2 2160 2280 2400 2640 2760 Low Vowel Sequence [a] [Ɔ] [o] [Ʊ] [u] Male F1 850 500 360 300 300 Female F1 1020 600 431 360 370 Male F2 1610 800 640 610 595 Female F2 1932 960 768 732 714 In the treadmill, F1 is descending while fo is ascending to produce a maximum number of harmonic/formant crossings. Figure 1 shows the graphic display for a D4–A4 up and down pentatonic scale (solid lines), combined with the low vowel formant frequencies (dashed lines). Note that there are [End Page 197] Click for larger view View full resolution Figure 1. Treadmill for the D4–A4 pentatonic scale produced on low vowels; (a) male sequence and (b) female sequence. five crossings on the ascending scale for both males and females. For males, the crossings are: fo crosses F1 near the [o] vowel; 2fo crosses F1 near the [Ɔ] vowel 2fo crosses F2 near the [o] vowel 3fo crosses F2 near the [Ɔ] vowel 4fo crosses F2 near the [Ɔ] vowel. Note the importance of the [Ɔ] and [o] vowels in males in this region of the pitch range. For females, the same five crossings occur, but on slightly more closed-mouth vowels due to higher overall formant frequencies. For example, fo crosses F1 closer to the [Ʊ] vowel than the [o] vowel. Figure 2 shows the treadmill for the high vowel sequence. The pentatonic scale is kept the same, D4–A4. There are now only two major crossings: fo crosses F1 between [e] and [I] in males and between [I] and [i] in females; 2fo crosses F2 between [æ] and [ɛ] in males and between [ɛ] and [e] in females None of the first 4 harmonics cross the second formant F2. Thus, in this region of the pitch range (D4–A4), acoustic registration in high vowels is carried primarily by the first two harmonics. The fifth and higher harmonics are not plotted. They will interact with F2 and higher formants, particularly if fo is raised. Figures 3 and 4 show the treadmills when the pentatonic scale is raised to the G4–D5 range. Usually one progresses in half-steps to this higher level. Most of the high pitch range for males and female belters is then covered. Figure 3 shows the low vowel sequence. The bright [a] vowel is now included in the crossings, but the general picture has not changed much from the A4–D4 scale. Of special...

Elucidating the role of adenine nucleotide transporter in mitochondrial swelling: an experimental and computational approaches

Mitochondria produce over 90% of cellular ATP and actively participate in maintaining ion homeostasis, redox status, lipid metabolism, and cell growth. Changes in the matrix volume of mitochondria affect their functional and structural integrity. Modest volume increases associated with modulation of the inner mitochondrial membrane can activate electron transfer chain and oxidative phosphorylation, whereas excessive swelling impairs structural organization of the membrane and initiate mitochondria‐mediated cell death mechanisms. Therefore, clarifying the precise mechanisms of excessive mitochondrial swelling is important for regulation of mitochondria‐mediated cell death pathways in response to energy and oxidative stresses. Opening of non‐selective mitochondrial permeability transition pores (mPTP) is the primary cause of excessive matrix swelling. The molecular identity remains unknown and recent studies suggest the existence of two or more types of mPTP that can be composed of different protein(s). The adenine nucleotide translocator (ANT) and FOF1‐ATP synthase were proposed to be potential mPTP core components that can act together or independently each other. Here, we elucidated the role of ANT in mPTP opening by applying both experimental and computational approaches. mPTP opening was evaluated in cardiac mitochondria that were exposed to moderate and high Ca2+ concentrations in the absence and presence of respiratory substrates and ADP. We developed a detailed model of the ANT transport mechanism including the matrix (ANTM), cytosolic (ANTC), and pore (ANTP) states of the transporter that was able to simulate our experimental data. In addition, we corroborated and simulated our ANT model based on previous ANT kinetics data. The model was successful not only in simulating ANT pore state transition, but also explained the potential role of ANT in mPTP opening in cardiac mitochondria.

Oriented Nanoarchitectonics of Bacteriorhodopsin for Enhancing ATP Generation in a Fo F1 -ATPase-Based Assembly System.

Energy conversion plays an important role in the metabolism of photosynthetic organisms. Improving energy transformation by promoting a proton gradient has been a great challenge for a long time. In the present study, we realize a directional proton migration through the construction of oriented bacteriorhodopsin (BR) microcapsules coated by Fo F1 -ATPase molecular motors through layer-by-layer (LBL) assembly. The changes in the conformation of BR under illumination lead to proton transfer in a radial direction, which generates a higher proton gradient to drive the synthesis of adenosine triphosphate (ATP) by Fo F1 -ATPase. Furthermore, to promote the photosynthetic activity, optically matched quantum dots were introduced into the artificial coassembly system of BR and Fo F1 -ATPase. Such a design creates a new path for the use of light energy.

Divergent Solid-Phase Synthesis and Biological Evaluation of Yaku'amide B and Its Seven E/Z Isomers.

Yaku'amide B (1) inhibits cancer cell growth through a unique mechanism of action. Compound 1 binds to mitochondrial Fo F1 -ATP synthase, inhibits ATP production, and enhances ATP hydrolysis. The presence of one (E)- and two (Z)-α,β-dehydroisoleucines (ΔIle) in the linear 13-mer sequence is the most unusual structural feature of 1. To uncover the biological importance of these residues, we synthesized 1 and its seven E/Z isomers 2-8 by devising a new divergent solid-phase strategy. Both the (E)- and (Z)-ΔIle residues were stereoselectively constructed by traceless Staudinger ligation on resin to ultimately deliver 1-8. All isomers 2-8 displayed effects on the inhibition of cell growth and ATP production, and enhanced ATP hydrolysis, thus indicating that 2-8 share the same mode of action as 1. The least potent isomer, 8, was isomeric at three ΔIle residues of the most potent 1. These findings together indicate that the E/Z stereochemistry of the three ΔIle residues controls the magnitude of the biological functions of 1.

Depletion of cardiolipin induces major changes in energy metabolism in Trypanosoma brucei bloodstream forms.

The mitochondrial inner membrane glycerophospholipid cardiolipin (CL) associates with mitochondrial proteins to regulate their activities and facilitate protein complex and supercomplex formation. Loss of CL leads to destabilized respiratory complexes and mitochondrial dysfunction. The role of CL in an organism lacking a conventional electron transport chain (ETC) has not been elucidated. Trypanosoma brucei bloodstream forms use an unconventional ETC composed of glycerol-3-phosphate dehydrogenase and alternative oxidase (AOX), while the mitochondrial membrane potential (ΔΨm) is generated by the hydrolytic action of the Fo F1 -ATP synthase (aka Fo F1 -ATPase). We now report that the inducible depletion of cardiolipin synthase (TbCls) is essential for survival of T brucei bloodstream forms. Loss of CL caused a rapid drop in ATP levels and a decline in the ΔΨm. Unbiased proteomic analyses revealed a reduction in the levels of many mitochondrial proteins, most notably of Fo F1 -ATPase subunits and AOX, resulting in a strong decline of glycerol-3-phosphate-stimulated oxygen consumption. The changes in cellular respiration preceded the observed decrease in Fo F1 -ATPase stability, suggesting that the AOX-mediated ETC is the first pathway responding to the decline in CL. Select proteins and pathways involved in glucose and amino acid metabolism were upregulated to counteract the CL depletion-induced drop in cellular ATP.

Cardiac metabolism as a driver and therapeutic target of myocardial infarction.

Reducing infarct size during a cardiac ischaemic‐reperfusion episode is still of paramount importance, because the extension of myocardial necrosis is an important risk factor for developing heart failure. Cardiac ischaemia‐reperfusion injury (IRI) is in principle a metabolic pathology as it is caused by abruptly halted metabolism during the ischaemic episode and exacerbated by sudden restart of specific metabolic pathways at reperfusion. It should therefore not come as a surprise that therapy directed at metabolic pathways can modulate IRI. Here, we summarize the current knowledge of important metabolic pathways as therapeutic targets to combat cardiac IRI. Activating metabolic pathways such as glycolysis (eg AMPK activators), glucose oxidation (activating pyruvate dehydrogenase complex), ketone oxidation (increasing ketone plasma levels), hexosamine biosynthesis pathway (O‐GlcNAcylation; administration of glucosamine/glutamine) and deacetylation (activating sirtuins 1 or 3; administration of NAD+‐boosting compounds) all seem to hold promise to reduce acute IRI. In contrast, some metabolic pathways may offer protection through diminished activity. These pathways comprise the malate‐aspartate shuttle (in need of novel specific reversible inhibitors), mitochondrial oxygen consumption, fatty acid oxidation (CD36 inhibitors, malonyl‐CoA decarboxylase inhibitors) and mitochondrial succinate metabolism (malonate). Additionally, protecting the cristae structure of the mitochondria during IR, by maintaining the association of hexokinase II or creatine kinase with mitochondria, or inhibiting destabilization of FOF1‐ATPase dimers, prevents mitochondrial damage and thereby reduces cardiac IRI. Currently, the most promising and druggable metabolic therapy against cardiac IRI seems to be the singular or combined targeting of glycolysis, O‐GlcNAcylation and metabolism of ketones, fatty acids and succinate.

Protein kinase Cα mediates recovery of renal and mitochondrial functions following acute injury.

Previously, we have shown that active protein kinase Cα (PKCα) promotes recovery of mitochondrial function after injury invitro [Nowak G & Bakajsova D (2012) Am J Physiol Renal Physiol 303, F515-F526]. This study examined whether PKCα regulates recovery of mitochondrial and kidney functions after ischemia-induced acute injury (AKI) invivo. Markers of kidney injury were increased after bilateral ischemia and returned to normal levels in wild-type (WT) mice. Maximum mitochondrial respiration and activities of respiratory complexes and Fo F1 -ATPase decreased after ischemia and recovered in WT mice. Reperfusion after ischemia was accompanied by translocation of active PKCα to mitochondria. PKCα deletion reduced mitochondrial respiration and activities of respiratory complex I and Fo F1 -ATPase in noninjured kidneys, indicating that PKCα is essential in developing fully functional renal mitochondria. These changes in PKCα-deficient mice were accompanied by lower levels of complex I subunits (NDUFA9 and NDUFS3) and the γ-subunit of Fo F1 -ATPase. Also, lack of PKCα exacerbated ischemia-induced decreases in respiration, complex I and Fo F1 -ATPase activities, and blocked their recovery after injury, indicating a crucial role of PKCα in promoting mitochondrial recovery after AKI. Further, PKCα deletion exacerbated acetylation and succinylation of key mitochondrial proteins of energy metabolism after ischemia due to decreases in deacetylase and desuccinylase (sirtuin3 and sirtuin5) levels in renal mitochondria. Thus, our data show a novel role for PKCα in regulating levels of mitochondrial sirtuins and acetylation and succinylation of key mitochondrial proteins. We conclude that PKCα deletion: (a) affects renal physiology by decreasing mitochondrial capacity for maximum respiration; (b) blocks recovery of mitochondrial functions, renal morphology, and functions after AKI; and (c) decreases survival after AKI. ENZYMES: Protein kinase C: EC 2.7.11.13; NADH:ubiquinone reductase (H+ -translocating; complex I): EC 7.1.1.2; FoF1-ATPase (H+ -transporting two-sector ATPase): EC 7.1.2.2; Succinate:ubiquinone oxidoreductase (complex II): EC 1.3.5.1; Ubiquinol:cytochrome-c reductase (complex III): EC 7.1.1.8; Cytochrome c oxidase (complex IV): EC 1.9.3.1; NAD-dependent protein deacetylase sirtuin-3, mitochondrial: EC 2.3.1.286; NAD-dependent protein deacetylase sirtuin-5, mitochondrial: EC 3.5.1.-; Proteinase K (peptidase K): EC 3.4.21.64.

C-terminal regulatory domain of the ε subunit of Fo F1 ATP synthase enhances the ATP-dependent H+ pumping that is involved in the maintenance of cellular membrane potential in Bacillus subtilis.

The ε subunit of FoF1‐ATPase/synthase (FoF1) plays a crucial role in regulating FoF1 activity. To understand the physiological significance of the ε subunit‐mediated regulation of FoF1 in Bacillus subtilis, we constructed and characterized a mutant harboring a deletion in the C‐terminal regulatory domain of the ε subunit (ε∆C). Analyses using inverted membrane vesicles revealed that the ε∆C mutation decreased ATPase activity and the ATP‐dependent H+‐pumping activity of FoF1. To enhance the effects of ε∆C mutation, this mutation was introduced into a ∆rrn8 strain harboring only two of the 10 rrn (rRNA) operons (∆rrn8 ε∆C mutant strain). Interestingly, growth of the ∆rrn8 ε∆C mutant stalled at late‐exponential phase. During the stalled growth phase, the membrane potential of the ∆rrn8 ε∆C mutant cells was significantly reduced, which led to a decrease in the cellular level of 70S ribosomes. The growth stalling was suppressed by adding glucose into the culture medium. Our findings suggest that the C‐terminal region of the ε subunit is important for alleviating the temporal reduction in the membrane potential, by enhancing the ATP‐dependent H+‐pumping activity of FoF1.

The plasma membrane H+ -ATPase, a simple polypeptide with a long history.

The plasma membrane H+‐ATPase of fungi and plants is a single polypeptide of fewer than 1,000 residues that extrudes protons from the cell against a large electric and concentration gradient. The minimalist structure of this nanomachine is in stark contrast to that of the large multi‐subunit FOF1 ATPase of mitochondria, which is also a proton pump, but under physiological conditions runs in the reverse direction to act as an ATP synthase. The plasma membrane H+‐ATPase is a P‐type ATPase, defined by having an obligatory phosphorylated reaction cycle intermediate, like cation pumps of animal membranes, and thus, this pump has a completely different mechanism to that of FOF1 ATPases, which operates by rotary catalysis. The work that led to these insights in plasma membrane H+‐ATPases of fungi and plants has a long history, which is briefly summarized in this review.

OSCP subunit of mitochondrial ATP synthase: role in regulation of enzyme function and of its transition to a pore.

The permeability transition pore (PTP) is a latent, high-conductance channel of the inner mitochondrial membrane. When activated, it plays a key role in cell death and therefore in several diseases. The investigation of the PTP took an unexpected turn after the discovery that cyclophilin D (the target of the PTP inhibitory effect of cyclosporin A) binds to FO F1 (F)-ATP synthase, thus inhibiting its catalytic activity by about 30%. This observation was followed by the demonstration that binding occurs at a particular subunit of the enzyme, the oligomycin sensitivity conferral protein (OSCP), and that F-ATP synthase can form Ca2+ -activated, high-conductance channels with features matching those of the PTP, suggesting that the latter originates from a conformational change in F-ATP synthase. This review is specifically focused on the OSCP subunit of F-ATP synthase, whose unique features make it a potential pharmacological target both for modulation of F-ATP synthase and its transition to a pore. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

The survival of irradiated lactobacilli in the simulated gastrointestinal conditions with antibiotic ceftazidime.

Lactobacillus acidophilus is one of the widespread probiotic bacteria that can overcome acid and bile barrier of stomach and intestine, respectively, and then have beneficial effects on the host improving its intestinal microbial balance. The cell membrane FO F1 -ATPase is an important factor in the response and tolerance to low pH through the action of controlling the H+ concentration between the cell cytoplasm and external medium. In this study, the effects of extremely high-frequency EMI at the frequencies of 51·8GHz and 53GHz and cetfazidime (μmol l-1 ) on survival of L. acidophilus VKM B-1660 in the gastrointestinal model invitro and on ATPase activity of their membrane vesicles were investigated. Irradiated L. acidophilus survived in media with acid pH; the irradiation stimulated N,N'-dicyclohexylcarbodiimide-sensitive FO F1 -ATPase activity under acidic conditions, but enhanced the inhibitory effects of ceftazidime. Probably irradiated L. acidophilus is overcoming the acid barrier even in the presence of ceftazidime due to the FO F1 -ATPase. The obtained results can allow the use of L. acidophilus in food industry, veterinary and medicine. SIGNIFICANCE AND IMPACT OF THE STUDY: The probiotic property of lactobacilli is defined with survival in different conditions of human digestive tract even in the presence of antibiotics and subjected to electromagnetic irradiation (EMI) at the extremely high frequency. Despite the fact that EMI and antibiotic ceftazidime affected Lactobacillus acidophilus; the viable number of bacterial cells was decreased in invitro gastrointestinal model, but they could to grow in fresh growth medium. The changes in the FO F1 -ATPase activity were obtained at acidic pH. Thus, these bacteria can overcome acid barrier due to the FO F1 -ATPase: the irradiation stimulates the FO F1 -ATPase activity in the acidic conditions, but enhances the effects of ceftazidime. The results are important for identifying the mechanisms of lactobacilli survival for physical and chemical factors and valuable for use.

Understanding the Role of Escherichia coli Hydrogenases and Formate Dehydrogenases in the FO F1 -ATPase Activity during the Mixed Acid Fermentation of Mixture of Carbon Sources.

During fermentation Escherichia coli produces di-hydrogen (H2 ) via reversible membrane-bound [Ni-Fe]-hydrogenases (Hyd). This study describes the total and N,N'-dicyclohexylcarbodiimide (DCCD) inhibited ATPase activity and H2 production at various pHs in E. coli wild type and mutants encoding Hyd enzymes and formate dehydrogenases (FDH) on fermentation of glucose, glycerol, and formate. The highest total ATPase activity was detected at pH 7.5 in hyaB hybC selC (lacking large subunits of Hyd-1 and Hyd-2 and FDH, respectively) triple mutant. This ATPase activity was mainly due to the proton-translocating ATPase but in FDH mutant the DCCD inhibition was less compared to wild type. Potassium ions stimulated total ATPase activity at pH 5.5 ~50% and ~35% in wild type and hypF (lacking all Hyd enzymes) mutant, respectively. Moreover, K+ also stimulated DCCD inhibited ATPase activity ~1.7-fold-2-fold in strains where FDH was absent only at pH 5.5. DCCD inhibited H2 production only at pH 5.5 in all assays. Taken together it is suggested that at low pH, FDH, and Hyd enzymes are linked with the FO F1 -ATPase for regulating and maintaining the cytoplasmatic pH and thus proton motive force generation. FDH and Hyd enzymes have impact on the FO F1 -ATPase activity depending on external pH and potassium ions. © 2018 IUBMB Life, 70(10):1040-1047, 2018.

Acid‐regulated gene expression of Helicobacter pylori: Insight into acid protection and gastric colonization

The pathogen Helicobacter pylori encounters many stressors as it transits to and infects the gastric epithelium. Gastric acidity is the predominate stressor encountered by the bacterium during initial infection and establishment of persistent infection. H.pylori initiates a rapid response to acid to maintain intracellular pH and proton motive force appropriate for a neutralophile. However, acid sensing by H.pylori may also serve as a transcriptional trigger to increase the levels of other pathogenic factors needed to subvert host defenses such as acid acclimation, antioxidants, flagellar synthesis and assembly, and CagA secretion. Helicobacter pylori were acid challenged at pH 3.0, 4.5, 6.0 vs nonacidic pH for 4 hours in the presence of urea, followed by RNA-seq analysis and qPCR. Cytoplasmic pH was monitored under the same conditions. About 250 genes were induced, and an equal number were repressed at acidic pHs. Genes encoding for antioxidant proteins, flagellar structural proteins, particularly class 2 genes, T4SS/Cag-PAI, Fo F1 -ATPase, and proteins involved in acid acclimation were highly expressed at acidic pH. Cytoplasmic pH decreased from 7.8 at pHout of 8.0 to 6.0 at pHout of 3.0. These results suggest that increasing extracellular or intracellular acidity or both are detected by the bacterium and serve as a signal to initiate increased production of protective and pathogenic factors needed to counter host defenses for persistent infection. These changes are dependent on degree of acidity and time of acid exposure, triggering a coordinated response to the environment required for colonization.

Identification of β-chain of Fo F1 -ATPase in apoptotic cell population induced by Microplitis bicoloratus bracovirus and its role in the development of Spodoptera litura.

Two physiological changes of Spodoptera litura parasitized by Microplitis bicoloratus are hemocyte-apoptosis and retarded immature development. β-Chain of Fo F1 -ATPase was found from a S. litura transcriptome. It belongs to a conserved P-loop NTPase superfamily, descending from a common ancestor of Lepidopteran clade. However, the characterization of β-chain of ATPase in apoptotic cells and its involvement in development remain unknown. Here, the ectopic expression and endogenous Fo F1 -ATPase β-chain occurred on S. litura cell membrane: in vivo, at the late stage of apoptotic hemocyte, endogenous Fo F1 -ATPase β-chain was stably expressed during M. bicoloratus larva development from 4 to 7 days post-parasitization; in vitro, at an early stage of pre-apoptotic Spli221 cells by infecting with M. bicoloratus bracovirus particles, the proteins were speedily recover expression. Furthermore, endogenous Fo F1 -ATPase β-chain was localized on the apoptotic cell membrane. RNA interference (RNAi) of Fo F1 -ATPase β-chain led to significantly decreased head capsule width. This suggested that Fo F1 -ATPase β-chain positively regulated the development of S. litura. The RNAi effect on the head capsule width was enhanced with parasitism. Our research found that Fo F1 -ATPase β-chain was expressed and localized on the cell membrane in the apoptotic cells, and involved in the development of S. litura.

Effect of polyphenolic phytochemicals on ectopic oxidative phosphorylation in rod outer segments of bovine retina.

The rod outer segments (OS) of the retina are specialized organelles where phototransduction takes place. The mitochondrial electron transport complexes I-IV, cytochrome c and Fo F1 -ATP synthase are functionally expressed in the OS disks. Here, we have studied the effect of some polyphenolic compounds acting as inhibitors of mitochondrial ATPase/synthase activity on the OS ectopic Fo F1 - ATP synthase. The mechanism of apoptosis in the OS was also investigated studying the expression of cytochrome c, caspase 9 and 3 and Apaf-1. We prepared OS from fresh bovine retinae. Semi-quantitative Western blotting, confocal and electron microscopy, and cytofluorimetry were used along with biochemical analyses such as oximetry, ATP synthesis and hydrolysis. Resveratrol and curcumin plus piperine inhibited ATP synthesis and oxygen consumption in the OS. Epigallocatechin gallate and quercetin inhibited ATP hydrolysis and oxygen consumption in the OS. Malondialdehyde and hydrogen peroxide were produced in respiring OS in the presence of substrates. Cytochrome c was located inside the disk membranes. Procaspase 9 and 3, as well as Apaf-1 were expressed in the OS. These polyphenolic phytochemicals modulated the Fo F1 -ATP synthase activity of the the OS reducing production of reactive oxygen intermediates by the OS ectopic electron transport chain. Polyphenols decrease membrane peroxidation and cytochrome c release from disks, preventing the induction of caspase-dependent apoptosis in the OS Such effects are relevant in the design of protection against functional impairment of the OS following oxidative stress from exposure to intense illumination.