scholarly journals Targeting the ATP Synthase in Staphylococcus aureus Small Colony Variants, Streptococcus pyogenes and Pathogenic Fungi

Antibiotics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 376
Author(s):  
Martin Vestergaard ◽  
Sahar Roshanak ◽  
Hanne Ingmer
Keyword(s):  
Atp Synthase ◽  
Streptococcus Pyogenes ◽  
Inhibitory Activity ◽  
Electron Transport Chain ◽  
Pathogenic Fungi ◽  
Polymyxin B ◽  
Small Colony Variants ◽  
Transport Chain ◽  
Oligomycin A ◽  
Small Colony

The ATP synthase has been validated as a druggable target with the approval of the ATP synthase inhibitor, bedaquiline, for treatment of drug-resistant Mycobacterium tuberculosis, a bacterial species in which the ATP synthase is essential for viability. Gene inactivation studies have also shown that the ATP synthase is essential among Streptococci, and some studies even suggest that inhibition of the ATP synthase is a strategy for the elimination of Staphylococcus aureus small colony variants with deficiencies in the electron transport chain, as well as pathogenic fungi, such as Candida albicans. Here we investigated five structurally diverse ATP synthase inhibitors, namely N,N′-dicyclohexylcarbodiimide (DCCD), oligomycin A, tomatidine, resveratrol and piceatannol, for their growth inhibitory activity against the bacterial strains Streptococcus pyogenes, S. aureus and two isogenic small colony variants, as well as the pathogenic fungal species, C. albicans and Aspergillus niger. DCCD showed broad-spectrum inhibitory activity against all the strains (minimum inhibitory concentration (MIC) 2–16 µg/mL), except for S. aureus, where the ATP synthase is dispensable for growth. Contrarily, oligomycin A selectively inhibited the fungal strains (MIC 1–8 µg/mL), while tomatidine showed very potent, but selective, activity against small colony variants of S. aureus with compromised electron transport chain activity (MIC 0.0625 µg/mL). Small colony variants of S. aureus were also more sensitive to resveratrol and piceatannol than the wild-type strain, and piceatannol inhibited S. pyogenes at 16–32 µg/mL. We previously showed that transposon inactivation of the ATP synthase sensitizes S. aureus towards polymyxin B and colistin, and here we demonstrate that treatment with structurally diverse ATP synthase inhibitors sensitized S. aureus towards polymyxin B. Collectively, our data show that ATP synthase inhibitors can have selective inhibitory activity against pathogenic microorganisms in which the ATP synthase is essential. The data also show that the inhibition of the ATP synthase in Streptococcus pyogenes may be a new strategy for development of a narrow-spectrum antibiotic class. In other major bacterial pathogens, such as S. aureus and potentially Escherichia coli, where the ATP synthase is dispensable, the ATP synthase inhibitors may be applied in combination with antimicrobial peptides to provide new therapeutic options.

Functional Expression of Electron Transport Chain and FoF1-ATP Synthase in Optic Nerve Myelin Sheath

2015 ◽  
Vol 40 (11) ◽  
pp. 2230-2241 ◽  
Author(s):  
Martina Bartolucci ◽  
Silvia Ravera ◽  
Greta Garbarino ◽  
Paola Ramoino ◽  
Sara Ferrando ◽  
...  
Keyword(s):  
Electron Transport ◽  
Optic Nerve ◽  
Atp Synthase ◽  
Myelin Sheath ◽  
Electron Transport Chain ◽  
Functional Expression ◽  
Transport Chain ◽  
Fof1 Atp Synthase

The efficiency and plasticity of mitochondrial energy transduction

2005 ◽  
Vol 33 (5) ◽  
pp. 897-904 ◽  
Author(s):  
M.D. Brand
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Uncoupling Protein ◽  
Coupling Efficiency ◽  
Energy Transduction ◽  
Proton Pumping ◽  
Complex Iii ◽  
Proton Pumps ◽  
Transport Chain

Since it was first realized that biological energy transduction involves oxygen and ATP, opinions about the amount of ATP made per oxygen consumed have continually evolved. The coupling efficiency is crucial because it constrains mechanistic models of the electron-transport chain and ATP synthase, and underpins the physiology and ecology of how organisms prosper in a thermodynamically hostile environment. Mechanistically, we have a good model of proton pumping by complex III of the electron-transport chain and a reasonable understanding of complex IV and the ATP synthase, but remain ignorant about complex I. Energy transduction is plastic: coupling efficiency can vary. Whether this occurs physiologically by molecular slipping in the proton pumps remains controversial. However, the membrane clearly leaks protons, decreasing the energy funnelled into ATP synthesis. Up to 20% of the basal metabolic rate may be used to drive this basal leak. In addition, UCP1 (uncoupling protein 1) is used in specialized tissues to uncouple oxidative phosphorylation, causing adaptive thermogenesis. Other UCPs can also uncouple, but are tightly regulated; they may function to decrease coupling efficiency and so attenuate mitochondrial radical production. UCPs may also integrate inputs from different fuels in pancreatic β-cells and modulate insulin secretion. They are exciting potential targets for treatment of obesity, cachexia, aging and diabetes.

Localized energy coupling during photophosphorylation by chromatophores of Rhodopseudomonas capsulata N22

1982 ◽  
Vol 2 (10) ◽  
pp. 743-749 ◽  
Author(s):  
G. Duncan Hitchens ◽  
Douglas B. Kell
Keyword(s):  
Free Energy ◽  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Energy Coupling ◽  
Rhodopseudomonas Capsulata ◽  
Titration Method ◽  
Dual Inhibitor ◽  
Transport Chain ◽  
Synthase Inhibitor

The principle of the dual inhibitor titration method for testing models of electron-transport phosphorylation is outlined, and the method is applied to the study of photophosphorylation in bacterial chromatophores. It is concluded that energy coupling is strictly localized in nature in this system, in the sense that free energy released by a particular electron-transport chain may be used only by a particular H+-ATP synthase. Dual inhibitor titrations using the uncoupler SF 6847 and the H+-ATP synthase inhibitor oligomycin indicate that uncouplers act by shuttling rapidly between the localized energy-coupling sites.

scholarly journals Functional characterization of mutants deficient in N-terminal phosphorylation of the CF1 subunit beta

2021 ◽  
Author(s):  
Ralph Bock ◽  
Deserah D Strand ◽  
Daniel Karcher ◽  
Stephanie Ruf ◽  
Anne Schadach ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Atp Hydrolysis ◽  
Molecular Motor ◽  
Functional Characterization ◽  
Phosphorylation Sites ◽  
Transport Chain

Understanding the regulation of photosynthetic light harvesting and electron transfer is of great importance to efforts to improve the ability of the electron transport chain to supply downstream metabolism. The central regulator of the electron transport chain is the ATP synthase, the molecular motor that harnesses the chemiosmotic potential generated from proton coupled electron transport to synthesize ATP. The ATP synthase is regulated both thermodynamically and post-translationally, with proposed phosphorylation sites on multiple subunits. In this study we focused on two N-terminal serines on the catalytic subunit beta, previously proposed to be important for dark inactivation of the complex to avoid ATP hydrolysis at night. Here we show that there is no clear role for phosphorylation in the dark inactivation of ATP synthase. Instead, mutation of one of the two phosphorylated serine residues to aspartate strongly decreased ATP synthase abundance. We propose that the loss of N-terminal phosphorylation of ATP beta may be involved in proper ATP synthase accumulation during complex assembly.

scholarly journals On the extent of localization of the energized membrane state in chromatophores from Rhodopseudomonas capsulata N22

1982 ◽  
Vol 206 (2) ◽  
pp. 351-357 ◽  
Author(s):  
G D Hitchens ◽  
D B Kell
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Relative Number ◽  
Coupling Model ◽  
Rhodopseudomonas Capsulata ◽  
Apparent Paradox ◽  
Model Free ◽  
Transport Chain ◽  
Chemiosmotic Coupling

1. The principle of the double-inhibitor titration method for assessing competing models of electron transport phosphorylation is expounded. 2. This principle is applied to photophosphorylation by chromatophores from Rhodopseudomonas capsulata N22. 3. It is found that, in contrast to the predictions of the chemiosmotic coupling model, free energy transfer is confined to individual electron transport chain and ATP synthase complexes. 4. This conclusion is not weakened by arguments concerning, the degree of uncoupling in the native chromatophore preparation or the relative number of electron transport chain and ATP synthase complexes present. 5. Photophosphorylation is completely inhibited by the uncoupler SF 6847 at a concentration corresponding to 0.31 molecules per electron transport chain. 6. The apparent paradox is solved by the proposal, consistent with the available evidence on the mode of action of uncouplers, that uncoupler binding causes a co-operative conformation transition in the chromatophore membrane, which leads to uncoupling and which is not present in the absence of uncoupler.

scholarly journals Regulation of COX Assembly and Function by Twin CX9C Proteins—Implications for Human Disease

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 197
Author(s):  
Stephanie Gladyck ◽  
Siddhesh Aras ◽  
Maik Hüttemann ◽  
Lawrence I. Grossman
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Atp Synthase ◽  
Protein Interactions ◽  
Human Disease ◽  
Electron Transport Chain ◽  
Intermembrane Space ◽  
Protein Protein Interactions ◽  
Inner Mitochondrial Membrane ◽  
Transport Chain

Oxidative phosphorylation is a tightly regulated process in mammals that takes place in and across the inner mitochondrial membrane and consists of the electron transport chain and ATP synthase. Complex IV, or cytochrome c oxidase (COX), is the terminal enzyme of the electron transport chain, responsible for accepting electrons from cytochrome c, pumping protons to contribute to the gradient utilized by ATP synthase to produce ATP, and reducing oxygen to water. As such, COX is tightly regulated through numerous mechanisms including protein–protein interactions. The twin CX9C family of proteins has recently been shown to be involved in COX regulation by assisting with complex assembly, biogenesis, and activity. The twin CX9C motif allows for the import of these proteins into the intermembrane space of the mitochondria using the redox import machinery of Mia40/CHCHD4. Studies have shown that knockdown of the proteins discussed in this review results in decreased or completely deficient aerobic respiration in experimental models ranging from yeast to human cells, as the proteins are conserved across species. This article highlights and discusses the importance of COX regulation by twin CX9C proteins in the mitochondria via COX assembly and control of its activity through protein–protein interactions, which is further modulated by cell signaling pathways. Interestingly, select members of the CX9C protein family, including MNRR1 and CHCHD10, show a novel feature in that they not only localize to the mitochondria but also to the nucleus, where they mediate oxygen- and stress-induced transcriptional regulation, opening a new view of mitochondrial-nuclear crosstalk and its involvement in human disease.

scholarly journals The Synthesis and Evaluation of Heterocycles as Anti-Tuberculosis Agents

2021 ◽  
Author(s):  
◽  
Kristiana Tika Santoso
Keyword(s):  
Cell Death ◽  
Natural Products ◽  
Electron Transport ◽  
Drug Development ◽  
Total Synthesis ◽  
Inhibitory Activity ◽  
Electron Transport Chain ◽  
Nadh Oxidation ◽  
Transport Chain ◽  
Mic Value

<p>Tuberculosis (TB) is the leading cause of death from a single infectious agent, Mycobacterium tuberculosis (Mtb), worldwide. Currently, the efficacy of TB treatment regimens has declined due to the rise in antibacterial resistance and the shortage of new TB drugs. Thus, much effort has been spent in anti-tuberculosis drug development and in identifying new therapeutic targets against Mtb. One such target is NADH dehydrogenase-II (NDH-II), an essential enzyme in the mycobacterial electron transport chain that is not present in mammalian cells. In this thesis, four classes of heterocyclic compounds that have the potential to target NDH-II and their evaluation as anti-tubercular agents, are described. An overview of TB drug development and NDH-II as a promising target for TB drugs are described in Chapter 1.  In Chapters 2 and 3, the potential of anti-tubercular drugs based on the quinolinequinone (QQ) scaffold is described. QQs have previously shown promise as TB drugs by activating NDH-II to overproduce harmful reactive oxygen species leading to bacterial cell death. Chapter 2 describes the total synthesis of the QQ natural products ascidiathiazone A and ascidiathiazone B, and derivatives thereof, using a synthetic route that allows for high divergency and the efficient synthesis of the natural products and their intermediates. To this end, the first total synthesis of ascidiathiazone B is reported, as is the identification of ascidiathiazone A as a promising anti-tuberculosis drug with an MIC of 1.6 μM against Mtb. Insight into the ability of a representative quinone, 7-chloro-6-chloroethylamino-2-methyl-QQ, to increase NDH-II activity is also described. In Chapter 3, the syntheses of thirty-two simplified QQs with different functional groups at the 6- and 7-positions of the QQ scaffold are described. These compounds were screened against Mtb, with the lead compound from this library, 7-chloro-6-propargylamino-QQ, exhibiting an MIC of 8 μM against Mtb. Structure-activity data revealed diminished biological activity for QQs bearing tertiary amines, as compared to those with secondary amines, suggesting that the presence of a hydrogen bond donor at the 6- and 7-positions of QQs may play a critical role in antimycobacterial activity.  In Chapter 4, the synthesis and anti-mycobacterial activity of chromonyl-pyrimidines is presented. Chromonyl-pyrimidines have a structural resemblance to quinolinyl pyrimidines, a class of known NDH-II inhibitors and anti-TB agents. Chromones have shown promise as TB drugs, though they have not yet been reported to bind NDH-II. Despite this, chromonyl-pyrimidines contain a ketone functionality that may be able to bind the quinone binding site. For the first eleven-member library of chromonyl pyrimidines synthesised, all but two of the compounds exhibited inhibitory activity against Mtb, however, the growth inhibition was modest (MIC = 36-684 M). Accordingly, a second generation of chromonyl pyrimidines was synthesised, which included six compounds with improved potency against Mtb – all with an MIC value of 12.5 μM. The activity of these chromonyl pyrimidines was attributed to the presence of aromatic rings both on the pyrimidine and the chromone scaffolds, though changes to the electronic properties of the aryl groups, i.e. the incorporations of electron-withdrawing and electron-donating groups, did not affect inhibitory activity.  Finally, in Chapter 5, a library of phthalazinones and pyrimidinyl-phthalazinones with anti-tubercular activity is described. While phthalazinones have not yet been extensively explored as anti-mycobacterial agents, the phthalazinone scaffold has the potential to act as an uncoupler. Uncouplers are typically weak acids or bases that act on the electron transport chain by dissipating the proton motive force and ultimately preventing the generation of ATP. In Mtb, this uncoupling process is detrimental and leads to cell death. Phthalazinones are weakly basic and, due to their bicyclic ketone-bearing motif, has the potential to bind NDH-II at the proposed Q-site. Accordingly, a series of phthalazinones was synthesised to investigate their anti-tubercular activity and uncoupling activity. From the library of phthalazinones, N-tert-butyl- and nitro-substituted phthalazinones elicited high inhibitory activity, both with an MIC value of 3 μM. Of particular note among the pyrimidinyl-phthalazinones was the 4-fluorophenyl-pyrimidinyl-N-heptyl phthalazinone, which showed high potency against Mtb with an MIC of 1.6 μM. Further biological studies showed that some phthalazinones increased the rate of NADH oxidation in mycobacteria, which could be a result of uncoupling activity, while a number of pyrimidinyl-phthalazinones decreased NADH oxidation rates. These mechanistic results indicated that the two classes of compounds may have different modes of inhibition.</p>

Downregulation of diaphragm electron transport chain and glycolytic enzyme gene expression in sepsis

2005 ◽  
Vol 99 (3) ◽  
pp. 1120-1126 ◽  
Author(s):  
Leigh Ann Callahan ◽  
Gerald S. Supinski
Keyword(s):  
Gene Expression ◽  
Energy Metabolism ◽  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Cellular Energy ◽  
Protein Levels ◽  
Cellular Energy Metabolism ◽  
Transport Chain ◽  
Genes Encoding

Cellular energy metabolism is altered in sepsis as a consequence of dysfunction of mitochondrial electron transport and glycolytic pathways. The purpose of the present study was to determine whether sepsis is associated with compensatory increases in gene expression of electron transport chain and glycolytic pathway proteins or, alternatively, whether gene expression decreases in sepsis, contributing to abnormalities in energy metabolism. Studies were performed using diaphragms from control and endotoxin-treated (8 mg·kg−1·day−1) rats; at 48 h after endotoxin administration, animals were killed. Microarrays and RNAse protection assays were used to assess the expression of several electron transport chain components (cytochrome- c oxidase subunits Cox 5A, Cox 5B, and Cox 6A, ATP synthase, and ATP synthase subunit 5B) and of the rate-limiting enzyme for glycolysis, phosphofructokinase (PFK). Western blotting was used to assess protein levels for these electron transport chain subunits and PFK. Activity assays were used to assess electron transport chain and phosphofructokinase function. We found that sepsis evoked 1) a downregulation of genes encoding all examined electron transport chain components (e.g., cytochrome- c oxidase 5A decreased 45 + 7%, P < 0.01) and PFK ( P < 0.001), 2) reductions in protein levels for these electron transport chain subunits and PFK ( P < 0.05 for each), and 3) decreases in mitochondrial state 3 respiration rates and phosphofructokinase enzyme activity ( P < 0.01 for each comparison). We speculate that these sepsis-induced reductions in the expression of genes encoding critical electron transport and glycolytic proteins contribute to the development and persistence of sepsis-induced abnormalities in cellular energy metabolism.

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