2-Aryl-Benzoimidazoles as Type II NADH Dehydrogenase Inhibitors of Mycobacterium tuberculosis.

The nonproton pumping type II NADH dehydrogenase in Mycobacterium tuberculosis is essential for meeting the energy needs in terms of ATP under normal aerobic and stressful hypoxic environmental states. Type II NADH dehydrogenase conduits electrons into the electron transport chain in Mycobacterium tuberculosis, which results in ATP synthesis. Therefore, the inhibition of NDH-2 ensures the abolishment of the entire ATP synthesis machinery. Also, type II NADH dehydrogenase is absent in the mammalian genome, thus making it a potential target for antituberculosis drug discovery. Herein, we have screened a commercially available library of drug-like molecules and have identified a hit having a benzimidazole core moiety (6, H37Rv mc26230; minimum inhibitory concentration (MIC) = 16 µg/mL and ATP IC50 = 0.23 µg/mL) interfering with the oxidative phosphorylation pathway. Extensive medicinal chemistry optimization resulted in analogue 8, with MIC = 4 µg/mL and ATP IC50 = 0.05 µg/mL against the H37Rv mc26230 strain of Mycobacterium tuberculosis. Compounds 6 and 8 were found to be active against mono- and multidrug-resistant mycobacterium strains and demonstrated a bactericidal response. The Peredox-mCherry experiment and identification of single-nucleotide polymorphisms in mutants of CBR-5992 (a known type II NADH dehydrogenase inhibitor) were used to confirm the molecules as inhibitors of the type II NADH dehydrogenase enzyme. The safety index >10 for the test active molecules revealed the safety of test molecules.

Decreased in Mitochondrial Complex I Subunit NDUFS2 Is Critical for Oocyte Quality During Postovulatory Aging in Pigs.

The levels of nicotinamide adenine dinucleotide (NADH) dehydrogenase [ubiquinone] iron-sulfur protein 2 (NDUFS2, a subunit of NADH dehydrogenase) decrease in aged tissues, and these reductions may be partly associated with age-related conditions such as Parkinson's disease. Aging leads to many mitochondrial defects, such as biogenesis disruption, dysfunction, defects in the mitochondrial membrane potential, and production of reactive oxygen species, that may be highly related to NDUFS2 expression. The relationship between NDUFS2 and postovulatory oocyte aging in pigs remains unknown. In this study, we investigated changes in NDUFS2 expression during postovulatory aging (POA). Furthermore, NDUFS2 was knocked down via dsRNA microinjection at the MII stage to evaluate the effects on mitochondrial-related processes during POA. The mRNA expression of NDUFS2 decreased significantly after 48-h aging compared with that in fresh oocytes. NDUFS2 knockdown (KD) significantly impaired the maintenance of oocyte morphology and blastocyst development of embryos after POA. The levels of PGC1α (mitochondrial biogenesis-related proteins) decreased significantly after NDUFS2 KD, while the level of GSNOR, a protein denitrosylase, was reduced by NDUFS2 KD after 48 h of aging. These data suggest that NDUFS2 is vital for maintaining the oocyte quality during POA in pigs.

Quinone chemistry in respiratory complex I involves protonation of a conserved aspartic acid residue.

Respiratory complex I is a central metabolic enzyme coupling NADH oxidation and quinone reduction with proton translocation. Despite the knowledge of the structure of the complex, the coupling of both processes is not entirely understood. Here, we use a combination of site-directed mutagenesis, biochemical assays, and redox-induced FTIR spectroscopy to demonstrate that the quinone chemistry includes the protonation and deprotonation of a specific, conserved aspartic acid residue in the quinone binding site (D325 on subunit NuoCD in Escherichia coli). Our experimental data support a proposal derived from theoretical considerations that deprotonation of this residue is involved in triggering proton translocation in respiratory complex I.

Improved fermentative gamma-aminobutyric acid production from glucose by the inactivation of respiratory chain components NDH-I and Cytbo3 in Escherichia coli.

Gamma-aminobutyric acid (GABA), which is synthesized from l-glutamic acid via glutamate decarboxylase (Gad), is used as food, supplements, and biodegradable plastics. Our previous study demonstrated an Escherichia coli mutant (ΔΔ) strain, lacking type I NADH dehydrogenase (NDH-I) and cytochrome bo3 oxidase (Cytbo3), produced 7 g/L glutamic acid on MS1 glucose-minimal medium. In this study, the ΔΔ strain was used for improving GABA production. A plasmid (pMBL19-gadB') expressing a mutated E. coli GadB (Glu89Gln/Δ452-466), retaining activity at neutral pH, was introduced into the ΔΔ strain and its parent strain (W1485). The ΔΔ strain carrying pMBL19-gadB' exhibited a twofold increase in GABA production compared to the W1485 strain carrying pMBL19-gadB'. Deleting the C-terminal (Δ471-511) of GadC antiporter in the ΔΔ strain further improved GABA yield by 1.5 g/L when cultured in MS1 glucose-minimal medium. On the other hand, a large amount of glutamic acid produced by the ΔΔ strain was not fully converted to GABA, likely due to the inhibition of GadB activity by the accumulation of acetic acid. Although there is room for improvement, these results indicate the efficacy of the ΔNDH-IΔCytbo3 double mutation in augmenting GABA production.

Fitness factors impacting survival of a subsurface bacterium in contaminated groundwater.

Many factors contribute to the ability of a microbial species to persist when encountering complexly contaminated environments, including time of exposure, the nature and concentration of contaminants, availability of nutritional resources, and possession of a combination of appropriate molecular mechanisms needed for survival. Herein we sought to identify genes that are most important for survival of Gram-negative Enterobacteriaceae in contaminated groundwater environments containing high concentrations of nitrate and metals using the metal-tolerant Oak Ridge Reservation isolate, Pantoea sp. MT58 (MT58). Survival fitness experiments in which a randomly barcoded transposon insertion (RB-TnSeq) library of MT58 was exposed directly to contaminated Oak Ridge Reservation groundwater samples from across a nitrate and mixed metal contamination plume were used to identify genes important for survival with increasing exposure times and concentrations of contaminants, and availability of a carbon source. Genes involved in controlling and using carbon, encoding transcriptional regulators, and related to Gram-negative outer membrane processes were among those found to be important for survival in contaminated Oak Ridge Reservation groundwater. A comparative genomics analysis of 75 Pantoea genus strains allowed us to further separate the survival determinants into core and non-core genes in the Pantoea pangenome, revealing insights into the survival of subsurface microorganisms during contaminant plume intrusion.

Discovery of antibacterial diketones against gram-positive bacteria.

The rapid rise of antibiotic resistance calls for the discovery of new antibiotics with distinct antibacterial mechanisms. New target mining is indispensable for developing antibiotics. Plant-microbial antibiotics are appealing to underexplored sources due to a dearth of comprehensive understanding of antibacterial activity and the excavation of new targets. Here, a series of phloroglucinol derivatives of plant-root-associated Pseudomonas fluorescens were synthesized for structure-activity relationship analysis. Notably, 2,4-diproylphloroglucinol (DPPG) displayed efficient bactericidal activity against a wide range of gram-positive bacteria. Importantly, mechanistic study exhibits that DPPG binds to type II NADH dehydrogenase (NDH-2), an essential enzyme catalyzing the transfer of electrons from NADH to quinones in the electron transport chain (ETC), blocking electron transfer in S. aureus. Last, we validated the efficacy of DPPG in vivo through animal infection models. Our findings not only provide a distinct antibiotic lead to treat multidrug resistant pathogens but also identify a promising antibacterial target.

Benign prostatic hyperplasia nodules in patients treated with celecoxib and/or finasteride have reduced levels of NADH dehydrogenase [ubiquinone] iron-sulfur protein 3, a mitochondrial protein essential for efficient function of the electron transport chain.

BACKGROUND: Benign prostatic hyperplasia (BPH) is a condition generally associated with advanced age in men that can be accompanied by bothersome lower urinary tract symptoms (LUTS) including intermittency, weak stream, straining, urgency, frequency, and incomplete bladder voiding. Pharmacotherapies for LUTS/BPH include alpha-blockers, which relax prostatic and urethral smooth muscle and 5ɑ-reductase inhibitors such as finasteride, which can block conversion of testosterone to dihydrotestosterone thereby reducing prostate volume. Celecoxib is a cyclooxygenase-2 inhibitor that reduces inflammation and has shown some promise in reducing prostatic inflammation and alleviating LUTS for some men with histological BPH. However, finasteride and celecoxib can reduce mitochondrial function in some contexts, potentially impacting their efficacy for alleviating BPH-associated LUTS. METHODS: To determine the impact of these pharmacotherapies on mitochondrial function in prostate tissues, we performed immunostaining of mitochondrial Complex I (CI) protein NADH dehydrogenase [ubiquinone] iron-sulfur protein 3 (NDUFS3) and inflammatory cells on BPH specimens from patients naïve to treatment, or who were treated with celecoxib and/or finasteride for 28 days, as well as prostate tissues from male mice treated with celecoxib or vehicle control for 28 days. Quantification and statistical correlation analyses of immunostaining were performed. RESULTS: NDUFS3 immunostaining was decreased in BPH compared to normal adjacent prostate. Patients treated with celecoxib and/or finasteride had significantly decreased NDUFS3 in both BPH and normal tissues, and no change in inflammatory cell infiltration compared to untreated patients. Mice treated with celecoxib also displayed a significant decrease in NDUFS3 immunostaining and no change in inflammatory cell infiltration. CONCLUSIONS: These findings suggest that celecoxib and/or finasteride are associated with an overall decrease in NDUFS3 levels in prostate tissues but do not impact the presence of inflammatory cells, suggesting a decline in mitochondrial CI function in the absence of enhanced inflammation. Given that BPH has recently been associated with increased prostatic mitochondrial dysfunction, celecoxib and/or finasteride may exacerbate existing mitochondrial dysfunction in some BPH patients thereby potentially limiting their overall efficacy in providing metabolic stability and symptom relief.

Structural robustness of the NADH binding site in NADH:ubiquinone oxidoreductase (complex I).

Energy converting NADH:ubiquinone oxidoreductase, complex I, is the first enzyme of respiratory chains in most eukaryotes and many bacteria. Mutations in genes encoding subunits of human complex I may lead to its dysfunction resulting in a diverse clinical pattern. The effect of mutations on the protein structure is not known. Here, we focus on mutations R88G, E246K, P252R and E377K that are found in subunit NDUFV1 comprising the NADH binding site of complex I. Homologous mutations were introduced into subunit NuoF of Aquifex aeolicus complex I and it was attempted to crystallize variants of the electron input module, NuoEF, with bound substrates in the oxidized and reduced state. The E377K variant did not form crystals most likely due to an improper protein assembly. The architecture of the NADH binding site is hardly affected by the other mutations indicating its unexpected structural robustness. The R88G, E246K and P252R mutations led to small local structural rearrangements that might be related to their pathogenicity. These minor structural changes involve substrate binding, product release and the putative formation of reactive oxygen species. The structural consequences of the mutations as obtained with the bacterial enzyme might thus help to contribute to the understanding of disease causing mutations.

Myricetin Acts as an Inhibitor of Type II NADH Dehydrogenase from Staphylococcus aureus.

BACKGROUND: Staphylococcus aureus is a common pathogenic microorganism in humans and animals. Type II NADH oxidoreductase (NDH-2) is the only NADH:quinone oxidoreductase present in this organism and represents a promising target for the development of anti-staphylococcal drugs. Recently, myricetin, a natural flavonoid from vegetables and fruits, was found to be a potential inhibitor of NDH-2 of S. aureus. The objective of this study was to evaluate the inhibitory properties of myricetin against NDH-2 and its impact on the growth and expression of virulence factors in S. aureus. RESULTS: A screening method was established to identify effective inhibitors of NDH-2, based on heterologously expressed S. aureus NDH-2. Myricetin was found to be an effective inhibitor of NDH-2 with a half maximal inhibitory concentration (IC50) of 2 µM. In silico predictions and enzyme inhibition kinetics further characterized myricetin as a competitive inhibitor of NDH-2 with respect to the substrate menadione (MK). The minimum inhibitory concentrations (MICs) of myricetin against S. aureus strains ranged from 64 to 128 µg/mL. Time-kill assays showed that myricetin was a bactericidal agent against S. aureus. In line with being a competitive inhibitor of the NDH-2 substrate MK, the anti-staphylococcal activity of myricetin was antagonized by MK-4. In addition, myricetin was found to inhibit the gene expression of enterotoxin SeA and reduce the hemolytic activity induced by S. aureus culture on rabbit erythrocytes in a dose-dependent manner. CONCLUSIONS: Myricetin was newly discovered to be a competitive inhibitor of S. aureus NDH-2 in relation to the substrate MK. This discovery offers a fresh perspective on the anti-staphylococcal activity of myricetin.

Synthesis and Anti-Chagas Activity Profile of a Redox-Active Lead 3-Benzylmenadione Revealed by High-Content Imaging.

Chagas disease, or American trypanosomiasis, is a neglected tropical disease which is a top priority target of the World Health Organization. The disease, endemic mainly in Latin America, is caused by the protozoan Trypanosoma cruzi and has spread around the globe due to human migration. There are multiple transmission routes, including vectorial, congenital, oral, and iatrogenic. Less than 1% of patients have access to treatment, relying on two old redox-active drugs that show poor pharmacokinetics and severe adverse effects. Hence, the priorities for the next steps of R&D include (i) the discovery of novel drugs/chemical classes, (ii) filling the pipeline with drug candidates that have new mechanisms of action, and (iii) the pressing need for more research and access to new chemical entities. In the present work, we first identified a hit (4a) with a potent anti-T. cruzi activity from a library of 3-benzylmenadiones. We then designed a synthetic strategy to build a library of 49 3-(4-monoamino)benzylmenadione derivatives via reductive amination to obtain diazacyclic benz(o)ylmenadiones. Among them, we identified by high content imaging an anti-amastigote "early lead" 11b (henceforth called cruzidione) revealing optimized pharmacokinetic properties and enhanced specificity. Studies in a yeast model revealed that a cruzidione metabolite, the 3-benzoylmenadione (cruzidione oxide), enters redox cycling with the NADH-dehydrogenase, generating reactive oxygen species, as hypothesized for the early hit (4a).

Scrutinizing a Lactococcus lactis mutant with enhanced capacity for extracellular electron transfer reveals a unique role for a novel type-II NADH dehydrogenase.

Lactococcus lactis, a lactic acid bacterium used in food fermentations and commonly found in the human gut, is known to possess a fermentative metabolism. L. lactis, however, has been demonstrated to transfer metabolically generated electrons to external electron acceptors, a process termed extracellular electron transfer (EET). Here, we investigated an L. lactis mutant with an unusually high capacity for EET that was obtained in an adaptive laboratory evolution (ALE) experiment. First, we investigated how global gene expression had changed, and found that amino acid metabolism and nucleotide metabolism had been affected significantly. One of the most significantly upregulated genes encoded the NADH dehydrogenase NoxB. We found that this upregulation was due to a mutation in the promoter region of NoxB, which abolished carbon catabolite repression. A unique role of NoxB in EET could be attributed and it was directly verified, for the first time, that NoxB could support respiration in L. lactis. NoxB, was shown to be a novel type-II NADH dehydrogenase that is widely distributed among gut microorganisms. This work expands our understanding of EET in Gram-positive electroactive microorganisms and the special significance of a novel type-II NADH dehydrogenase in EET.IMPORTANCEElectroactive microorganisms with extracellular electron transfer (EET) ability play important roles in biotechnology and ecosystems. To date, there have been many investigations aiming at elucidating the mechanisms behind EET, and determining the relevance of EET for microorganisms in different niches. However, how EET can be enhanced and harnessed for biotechnological applications has been less explored. Here, we compare the transcriptomes of an EET-enhanced L. lactis mutant with its parent and elucidate the underlying reason for its superior performance. We find that one of the most significantly upregulated genes is the gene encoding the NADH dehydrogenase NoxB, and that upregulation is due to a mutation in the catabolite-responsive element that abolishes carbon catabolite repression. We demonstrate that NoxB has a special role in EET, and furthermore show that it supports respiration to oxygen, which has never been done previously. In addition, a search reveals that this novel NoxB-type NADH dehydrogenase is widely distributed among gut microorganisms.

Enhanced Reduction of Ferredoxin in PGR5-Deficient Mutant of Arabidopsis thaliana Stimulated Ferredoxin-Dependent Cyclic Electron Flow around Photosystem I.

The molecular entity responsible for catalyzing ferredoxin (Fd)-dependent cyclic electron flow around photosystem I (Fd-CEF) remains unidentified. To reveal the in vivo molecular mechanism of Fd-CEF, evaluating ferredoxin reduction-oxidation kinetics proves to be a reliable indicator of Fd-CEF activity. Recent research has demonstrated that the expression of Fd-CEF activity is contingent upon the oxidation of plastoquinone. Moreover, chloroplast NAD(P)H dehydrogenase does not catalyze Fd-CEF in Arabidopsis thaliana. In this study, we analyzed the impact of reduced Fd on Fd-CEF activity by comparing wild-type and pgr5-deficient mutants (pgr5hope1). PGR5 has been proposed as the mediator of Fd-CEF, and pgr5hope1 exhibited a comparable CO2 assimilation rate and the same reduction-oxidation level of PQ as the wild type. However, P700 oxidation was suppressed with highly reduced Fd in pgr5hope1, unlike in the wild type. As anticipated, the Fd-CEF activity was enhanced in pgr5hope1 compared to the wild type, and its activity further increased with the oxidation of PQ due to the elevated CO2 assimilation rate. This in vivo research clearly demonstrates that the expression of Fd-CEF activity requires not only reduced Fd but also oxidized PQ. Importantly, PGR5 was found to not catalyze Fd-CEF, challenging previous assumptions about its role in this process.

Structures of 3-acetylpyridine adenine dinucleotide and ADP-ribose bound to the electron input module of respiratory complex I.

Energy-converting NADH:ubiquinone oxidoreductase, respiratory complex I, is a major enzyme of energy metabolism that couples NADH oxidation and ubiquinone reduction with proton translocation. The NADH oxidation site features different enzymatic activities with various nucleotides. While the kinetics of these reactions are well described, only binding of NAD+ and NADH have been structurally characterized. Here, we report the structures of the electron input module of Aquifex aeolicus complex I with bound ADP-ribose and 3-acetylpyridine adenine dinucleotides at resolutions better than 2.0 Å. ADP-ribose acts as inhibitor by blocking the "ADP-handle" motif essential for nucleotide binding. The pyridine group of APADH is minimally offset from flavin, which could contribute to its poorer suitability as substrate. A comparison with other nucleotide co-structures surprisingly shows that the adenine ribose and the pyrophosphate moiety contribute most to nucleotide binding, thus all adenine dinucleotides share core binding modes to the unique Rossmann-fold in complex I.

Mitochondrial complex I inhibition triggers NAD+-independent glucose oxidation via successive NADPH formation, "futile" fatty acid cycling, and FADH2 oxidation.

Inhibition of mitochondrial complex I (NADH dehydrogenase) is the primary mechanism of the antidiabetic drug metformin and various unrelated natural toxins. Complex I inhibition can also be induced by antidiabetic PPAR agonists, and it is elicited by methionine restriction, a nutritional intervention causing resistance to diabetes and obesity. Still, a comprehensible explanation to why complex I inhibition exerts antidiabetic properties and engenders metabolic inefficiency is missing. To evaluate this issue, we have systematically reanalyzed published transcriptomic datasets from MPP-treated neurons, metformin-treated hepatocytes, and methionine-restricted rats. We found that pathways leading to NADPH formation were widely induced, together with anabolic fatty acid biosynthesis, the latter appearing highly paradoxical in a state of mitochondrial impairment. However, concomitant induction of catabolic fatty acid oxidation indicated that complex I inhibition created a "futile" cycle of fatty acid synthesis and degradation, which was anatomically distributed between adipose tissue and liver in vivo. Cofactor balance analysis unveiled that such cycling would indeed be energetically futile (-3 ATP per acetyl-CoA), though it would not be redox-futile, as it would convert NADPH into respirable FADH2 without any net production of NADH. We conclude that inhibition of NADH dehydrogenase leads to a metabolic shift from glycolysis and the citric acid cycle (both generating NADH) towards the pentose phosphate pathway, whose product NADPH is translated 1:1 into FADH2 by fatty acid cycling. The diabetes-resistant phenotype following hepatic and intestinal complex I inhibition is attributed to FGF21- and GDF15-dependent fat hunger signaling, which remodels adipose tissue into a glucose-metabolizing organ.

Molecular discrimination of G1 and G3 genotypes of Echinococcus granulosus sensu stricto obtained from human, cattle, and sheep using the mitochondrial NADH dehydrogenase subunit 5 marker.

Cystic echinococcosis (CE) is a common zoonotic disease caused by the larval form of Echinococcus granulosus sensu lato. This study determined the genotype and haplotype differences using the NADH dehydrogenase subunit 5 gene in hydatid cyst samples. Human (n = 12), cattle (n = 28), and sheep (n = 31) hydatid cyst isolates were included. Seventy-one genomic DNA samples were successfully extracted, and a 759 bp mitochondrial NADH dehydrogenase subunit 5 gene fragment was amplified by PCR. Following the sequence analysis, E. granulosus sensu stricto isolates were identified as G1 (n = 61) and G3 (n = 10). A total of 23 haplotypes were obtained from the 71 E. granulosus s.s. G1 and G3 samples. The main haplotype was Hap01 (60.56 %), which consisted of the G1 genotype. The second largest haplotype was Hap04, which consisted entirely of the G3 genotype. Hap14 acted as a bridge between the G1 and G3 genotypes. This study identifies G1 as the dominant genotype in humans and farm animals in Turkey. High haplotype and nucleotide diversity in genotypes were observed. Additionally, this is the first report on the phylogeography and gene flow models of the E. granulosus s.s. population in Turkey using the NADH dehydrogenase subunit 5 gene, the best marker distinguishing between G1 and G3 genotypes.

Oxidase enzyme genes are differentially expressed during Acanthamoeba castellanii encystment.

Acanthamoeba castellanii, a ubiquitous protozoan, is responsible for significant diseases such as Acanthamoeba keratitis and granulomatous amoebic encephalitis. A crucial survival strategy of A. castellanii involves the formation of highly resistant cysts during adverse conditions. This study delves into the cellular processes underpinning encystment, focusing on gene expression changes related to reactive oxygen species (ROS) balance, with a particular emphasis on mitochondrial processes. Our findings reveal a dynamic response within the mitochondria during encystment, with the downregulation of key enzymes involved in oxidative phosphorylation (COX, AOX, and NADHalt) during the initial 48 h, followed by their overexpression at 72 h. This orchestrated response likely creates a pro-oxidative environment, facilitating encystment. Analysis of other ROS processing enzymes across the cell reveals differential expression patterns. Notably, antioxidant enzymes, such as catalases, glutaredoxins, glutathione S-transferases, peroxiredoxins, and thioredoxins, mirror the mitochondrial trend of downregulation followed by upregulation. Additionally, glycolysis and gluconeogenesis are downregulated during the early stages in order to potentially balance the metabolic requirement of the cyst. Our study underscores the importance of ROS regulation in Acanthamoeba encystment. Understanding these mechanisms offers insights into infection control and identifies potential therapeutic targets. This work contributes to unraveling the complex biology of A. castellanii and may aid in combatting Acanthamoeba-related infections. Further research into ROS and oxidase enzymes is warranted, given the organism's remarkable respiratory versatility.

Reduced mitochondrial-encoded NADH dehydrogenase 6 gene expression drives inflammatory CD4+T cells in patients with systemic lupus erythematosus.

Abnormal mitochondrial function has been implicated in the progression of systemic lupus erythematosus (SLE), the prototypical autoimmune disease, yet the underlying cause remains unclear. In this study, mitochondrial-encoded NADH dehydrogenase 6 gene (MT-ND6) was identified as having increased m6A methylation and decreased expression in peripheral blood mononuclear cells of SLE patients by MeRIP-seq analysis. MT-ND6 expression was negatively correlated with SLE disease activity index score and 24-h urine protein level, and lower in patients with positive anti-Sm or anti-dsDNA antibodies. With the reduction of MT-ND6 levels, CD4+ T cells in SLE patients exhibited mitochondrial dysfunction, as evidenced by increased levels of reactive oxygen species (ROS) and mitochondrial ROS and insufficient ATP production. Accordingly, in vitro MT-ND6 silencing induced abnormalities in the above mitochondrial indicators in CD4+ T cells, and promoted the development of both transcription and inflammatory factors in these cells. In contrast, treatment with targeted mitochondrial antioxidants largely counteracted the silencing effect of MT-MD6. Thus, reduced MT-ND6 in SLE patients may lead to mitochondrial dysfunction through ROS overproduction, thereby promoting inflammatory CD4+ T cells.

Promotion of oxidative phosphorylation by complex I-anchored carbonic anhydrases?

The mitochondrial NADH-dehydrogenase complex of the respiratory chain, known as complex I, includes a carbonic anhydrase (CA) module attached to its membrane arm on the matrix side in protozoans, algae, and plants. Its physiological role is so far unclear. Recent electron cryo-microscopy (cryo-EM) structures show that the CA module may directly provide protons for translocation across the inner mitochondrial membrane at complex I. CAs can have a central role in adjusting the proton concentration in the mitochondrial matrix. We suggest that CA anchoring in complex I represents the original configuration to secure oxidative phosphorylation (OXPHOS) in the context of early endosymbiosis. After development of 'modern mitochondria' with pronounced cristae structures, this anchoring became dispensable, but has been retained in protozoans, algae, and plants.

Mitochondrial Oxidative Phosphorylation in Viral Infections.

Mitochondria have been identified as the "powerhouse" of the cell, generating the cellular energy, ATP, for almost seven decades. Research over time has uncovered a multifaceted role of the mitochondrion in processes such as cellular stress signaling, generating precursor molecules, immune response, and apoptosis to name a few. Dysfunctional mitochondria resulting from a departure in homeostasis results in cellular degeneration. Viruses hijack host cell machinery to facilitate their own replication in the absence of a bonafide replication machinery. Replication being an energy intensive process necessitates regulation of the host cell oxidative phosphorylation occurring at the electron transport chain in the mitochondria to generate energy. Mitochondria, therefore, can be an attractive therapeutic target by limiting energy for viral replication. In this review we focus on the physiology of oxidative phosphorylation and on the limited studies highlighting the regulatory effects viruses induce on the electron transport chain.

Noncoupled Mitochondrial Respiration as Therapeutic Approach for the Treatment of Metabolic Diseases: Focus on Transgenic Animal Models.

Mitochondrial dysfunction contributes to numerous chronic diseases, and mitochondria are targets for various toxins and xenobiotics. Therefore, the development of drugs or therapeutic strategies targeting mitochondria is an important task in modern medicine. It is well known that the primary, although not the sole, function of mitochondria is ATP generation, which is achieved by coupled respiration. However, a high membrane potential can lead to uncontrolled reactive oxygen species (ROS) production and associated dysfunction. For over 50 years, scientists have been studying various synthetic uncouplers, and for more than 30 years, uncoupling proteins that are responsible for uncoupled respiration in mitochondria. Additionally, the proteins of the mitochondrial alternative respiratory pathway exist in plant mitochondria, allowing noncoupled respiration, in which electron flow is not associated with membrane potential formation. Over the past two decades, advances in genetic engineering have facilitated the creation of various cellular and animal models that simulate the effects of uncoupled and noncoupled respiration in different tissues under various disease conditions. In this review, we summarize and discuss the findings obtained from these transgenic models. We focus on the advantages and limitations of transgenic organisms, the observed physiological and biochemical changes, and the therapeutic potential of uncoupled and noncoupled respiration.