Studies on inhibition of respiratory cytochrome bc1 complex by the fungicide pyrimorph suggest a novel inhibitory mechanism

Triphenylphosphonium (TPP)-Conjugated Quinolone Analogs Displayed Significantly Enhanced Fungicidal Activity Superior to Its Parent Molecule

Although 1-hydroxy-4-quinolone derivatives, such as 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO), aurachin C, and floxacrine, have been reported as effective cytochrome bc₁ complex inhibitors, the bioactivity of these products is not ideal, presumably due to their low bioavailability in tissues, particularly their poor solubility and low mitochondrial accumulation. In order to overcome the drawbacks of these compounds and develop their use as agricultural fungicides acting by cytochrome bc₁ inhibition, in this study, three novel mitochondria-targeting quinolone analogs (mitoQNOs) were designed and synthesized by conjugating triphenylphosphonium (TPP) with quinolone. They exhibited greatly enhanced fungicidal activity compared to the parent molecule, especially mitoQNO₁₁, which showed high antifungal activity against Phytophthora capsici and Sclerotinia sclerotiorum with EC₅₀ values of 7.42 and 4.43 μmol/L, respectively. In addition, mitoQNO₁₁ could inhibit the activity of the cytochrome bc₁ complex of P. capsici in a dose-dependent manner and effectively depress its respiration and ATP production. The greatly decreased mitochondrial membrane potential and massively generated reactive oxygen species (ROS) strongly suggested that the inhibition of complex III led to the leakage of free electrons, which resulted in the damage of the pathogen cell structure. The results of this study indicated that TPP-conjugated QNOs might be used as agricultural fungicides by conjugating them with TPP.

Insecticidal activity of essential oils from American native plants against Aedes aegypti (Diptera: Culicidae): an introduction to their possible mechanism of action

Searching for new bioactive molecules to design insecticides is a complex process since pesticides should be highly selective, active against the vector, and bio-safe for humans. Aiming to find natural compounds for mosquito control, we evaluated the insecticidal activity of essential oils (EOs) from 20 American native plants against Aedes aegypti larvae using bioassay, biochemical, and in silico analyses. The highest larvicide activity was exhibited by EOs from Steiractinia aspera (LC₅₀ = 42.4 µg/mL), Turnera diffusa (LC₅₀ = 70.9 µg/mL), Piper aduncum (LC₅₀ = 55.8 µg/mL), Lippia origanoides (chemotype thymol/carvacrol) (LC₅₀ = 61.9 µg/mL), L. origanoides (chemotype carvacrol/thymol) (LC₅₀ = 59.8 µg/mL), Hyptis dilatata (LC₅₀ = 61.1 µg/mL), Elaphandra quinquenervis (LC₅₀ = 61.1 µg/mL), and Calycolpus moritzianus (LC₅₀ = 73.29 µg/mL) after 24 h. This biological activity may be related to the disruption of the electron transport chain through the mitochondrial protein complexes. We hypothesized that the observed EOs' effect is due to their major components, where computational approaches such as homology modeling and molecular docking may suggest the possible binding pose of secondary metabolites that inhibit the mitochondrial enzymes and acetylcholinesterase activity (AChE). Our results provided insights into the possible mechanism of action of EOs and their major compounds for new insecticide designs targeting the mitochondria and AChE activity in A. aegypti for effective and safe insecticide.

Triphenylphosphonium-Driven Targeting of Pyrimorph Fragment Derivatives Greatly Improved Its Action on Phytopathogen Mitochondria

Pyrimorph is a carboxylic acid amide (CAA) fungicide, which shows excellent activity against oomycetes such as pepper phytophthora blight, tomato late blight, and downy mildew of cucumber. It works mainly by inhibiting the biosynthesis of cell wall of oomycetes. However, pyrimorph also shows weak activity of inhibiting mitochondrial complex III, which is the first CAA fungicide found to act on mitochondria. To improve this effect on mitochondria and develop fungicides that may have a novel mechanism of action, in this paper, by disassembling pyrimorph and conjugating the fragments with the mitochondrial-targeted delivery system (triphenylphosphonium), three series of mitochondrial-targeting analogues of pyrimorph were designed and synthesized. The results show that the pyridine-containing 1,1-diaryl is the core module of inhibition mitochondrial function of pyrimorph. Among these conjugates, compound 3b with a short linker showed the highest and broad-spectrum fungicidal activity, strong respiratory inhibition activity, and adenosine 5'-triphosphate synthesis inhibition activity, suggesting its potential as a fungicide candidate. 3b exhibited greatly improved action on mitochondria, such as by destroying the mitochondrial function of pathogens, causing mitochondrial swelling, weakening its influence on cell wall morphology, and so on. More importantly, this study provides a method to strengthen the drugs or pesticides with weak mitochondrial action, which is of special significance for developing mitochondrial bioactive molecules with the novel action mechanism.

Metabolomics-Based Mechanistic Insights into Revealing the Adverse Effects of Pesticides on Plants: An Interactive Review

In plant biology, metabolomics is often used to quantitatively assess small molecules, metabolites, and their intermediates in plants. Metabolomics has frequently been applied to detect metabolic alterations in plants exposed to various biotic and abiotic stresses, including pesticides. The widespread use of pesticides and agrochemicals in intensive crop production systems is a serious threat to the functionality and sustainability of agroecosystems. Pesticide accumulation in soil may disrupt soil-plant relationships, thereby posing a pollution risk to agricultural output. Application of metabolomic techniques in the assessment of the biological consequences of pesticides at the molecular level has emerged as a crucial technique in exposome investigations. State-of-the-art metabolomic approaches such as GC-MS, LC-MS/MS UHPLC, UPLC-IMS-QToF, GC/EI/MS, MALDI-TOF MS, and ¹H-HR-MAS NMR, etc., investigating the harmful effects of agricultural pesticides have been reviewed. This updated review seeks to outline the key uses of metabolomics related to the evaluation of the toxicological impacts of pesticides on agronomically important crops in exposome assays as well as bench-scale studies. Overall, this review describes the potential uses of metabolomics as a method for evaluating the safety of agricultural chemicals for regulatory applications. Additionally, the most recent developments in metabolomic tools applied to pesticide toxicology and also the difficulties in utilizing this approach are discussed.

Deletion of the PA4427-PA4431 Operon of Pseudomonas aeruginosa PAO1 Increased Antibiotics Resistance and Reduced Virulence and Pathogenicity by Affecting Quorum Sensing and Iron Uptake

The respiratory chain is very important for bacterial survival and pathogenicity, yet the roles of the respiratory chain in P. aeruginosa remain to be fully elucidated. Here, we not only proved experimentally that the operon PA4427-PA4431 of Pseudomonas aeruginosa PAO1 encodes respiratory chain complex III (cytobc1), but also found that it played important roles in virulence and pathogenicity. PA4429–31 deletion reduced the production of the virulence factors, including pyocyanin, rhamnolipids, elastase, and extracellular polysaccharides, and it resulted in a remarkable decrease in pathogenicity, as demonstrated in the cabbage and Drosophila melanogaster infection models. Furthermore, RNA-seq analysis showed that PA4429–31 deletion affected the expression levels of the genes related to quorum-sensing systems and the transport of iron ions, and the iron content was also reduced in the mutant strain. Taken together, we comprehensively illustrated the function of the operon PA4427–31 and its application potential as a treatment target in P. aeruginosa infection.

Mesorhizobium ciceri as biological tool for improving physiological, biochemical and antioxidant state of Cicer aritienum (L.) under fungicide stress

Fungicides among agrochemicals are consistently used in high throughput agricultural practices to protect plants from damaging impact of phytopathogens and hence to optimize crop production. However, the negative impact of fungicides on composition and functions of soil microbiota, plants and via food chain, on human health is a matter of grave concern. Considering such agrochemical threats, the present study was undertaken to know that how fungicide-tolerant symbiotic bacterium, Mesorhizobium ciceri affects the Cicer arietinum crop while growing in kitazin (KITZ) stressed soils under greenhouse conditions. Both in vitro and soil systems, KITZ imparted deleterious impacts on C. arietinum as a function of dose. The three-time more of normal rate of KITZ dose detrimentally but maximally reduced the germination efficiency, vigor index, dry matter production, symbiotic features, leaf pigments and seed attributes of C. arietinum. KITZ-induced morphological alterations in root tips, oxidative damage and cell death in root cells of C. arietinum were visible under scanning electron microscope (SEM). M. ciceri tolerated up to 2400 µg mL-1 of KITZ, synthesized considerable amounts of bioactive molecules including indole-3-acetic-acid (IAA), 1-aminocyclopropane 1-carboxylate (ACC) deaminase, siderophores, exopolysaccharides (EPS), hydrogen cyanide, ammonia, and solubilised inorganic phosphate even in fungicide-stressed media. Following application to soil, M. ciceri improved performance of C. arietinum and enhanced dry biomass production, yield, symbiosis and leaf pigments even in a fungicide-polluted environment. At 96 µg KITZ kg-1 soil, M. ciceri maximally and significantly (p ≤ 0.05) augmented the length of plants by 41%, total dry matter by 18%, carotenoid content by 9%, LHb content by 21%, root N by 9%, shoot P by 11% and pod yield by 15% over control plants. Additionally, the nodule bacterium M. ciceri efficiently colonized the plant rhizosphere/rhizoplane and considerably decreased the levels of stressor molecules (proline and malondialdehyde) and antioxidant defence enzymes viz. ascorbate peroxidise (APX), guaiacol peroxidise (GPX), catalase (CAT) and peroxidises (POD) of C. arietinum plants when inoculated in soil. The symbiotic strain effectively colonized the plant rhizosphere/rhizoplane. Conclusively, the ability to endure higher fungicide concentrations, capacity to secrete plant growth modulators even under fungicide pressure, and inherent features to lower the level of proline and plant defence enzymes makes this M. ciceri as a superb choice for augmenting the safe production of C. arietinum even under fungicide-contaminated soils.

Catalytic Reactions and Energy Conservation in the Cytochrome bc1 and b6f Complexes of Energy-Transducing Membranes

This review focuses on key components of respiratory and photosynthetic energy-transduction systems: the cytochrome bc1 and b6f (Cytbc1/b6f) membranous multisubunit homodimeric complexes. These remarkable molecular machines catalyze electron transfer from membranous quinones to water-soluble electron carriers (such as cytochromes c or plastocyanin), coupling electron flow to proton translocation across the energy-transducing membrane and contributing to the generation of a transmembrane electrochemical potential gradient, which powers cellular metabolism in the majority of living organisms. Cytsbc1/b6f share many similarities but also have significant differences. While decades of research have provided extensive knowledge on these enzymes, several important aspects of their molecular mechanisms remain to be elucidated. We summarize a broad range of structural, mechanistic, and physiological aspects required for function of Cytbc1/b6f, combining textbook fundamentals with new intriguing concepts that have emerged from more recent studies. The discussion covers but is not limited to (i) mechanisms of energy-conserving bifurcation of electron pathway and energy-wasting superoxide generation at the quinol oxidation site, (ii) the mechanism by which semiquinone is stabilized at the quinone reduction site, (iii) interactions with substrates and specific inhibitors, (iv) intermonomer electron transfer and the role of a dimeric complex, and (v) higher levels of organization and regulation that involve Cytsbc1/b6f. In addressing these topics, we point out existing uncertainties and controversies, which, as suggested, will drive further research in this field.

Crystal structure of bacterial cytochrome bc 1 in complex with azoxystrobin reveals a conformational switch of the Rieske iron-sulfur protein subunit

Cytochrome bc ₁ complexes (cyt bc ₁), also known as complex III in mitochondria, are components of the cellular respiratory chain and of the photosynthetic apparatus of non-oxygenic photosynthetic bacteria. They catalyze electron transfer (ET) from ubiquinol to cytochrome c and concomitantly translocate protons across the membrane, contributing to the cross-membrane potential essential for a myriad of cellular activities. This ET-coupled proton translocation reaction requires a gating mechanism that ensures bifurcated electron flow. Here, we report the observation of the Rieske iron-sulfur protein (ISP) in a mobile state, as revealed by the crystal structure of cyt bc ₁ from the photosynthetic bacterium Rhodobacter sphaeroides in complex with the fungicide azoxystrobin. Unlike cyt bc ₁ inhibitors stigmatellin and famoxadone that immobilize the ISP, azoxystrobin causes the ISP-ED to separate from the cyt b subunit and to remain in a mobile state. Analysis of anomalous scattering signals from the iron-sulfur cluster of the ISP suggests the existence of a trajectory for electron delivery. This work supports and solidifies the hypothesis that the bimodal conformation switch of the ISP provides a gating mechanism for bifurcated ET, which is essential to the Q-cycle mechanism of cyt bc ₁ function.

In vitro investigation to explore the toxicity of different groups of pesticides for an agronomically important rhizosphere isolate Azotobacter vinelandii

In this work, an attempt was made to evaluate the effect of pesticides on growth pattern, surface morphology, cell viability and growth regulators of nitrogen fixing soil bacterium. Pesticide tolerant Azotobacter vinelandii strain AZ6 (Accession no. MG028654) was found to tolerate maximum level of pesticide and displayed multifarious PGP activities. At higher concentrations, pesticides triggered cellular/structural damage and reduced the cell viability as clearly shown under SEM and CLSM. With increase in concentration, pesticides exhibited a significant (p < 0.05) decrease in PGP traits of strain AZ6. Among all three groups of pesticides, herbicides glyphosate and atrazine were most toxic. Kitazin, hexaconazole, metalaxyl, glyphosate, quizalofop, atrazine, fipronil, monocrotophos and imidacloprid at 2400, 1800, 1500, 900, 1200, 900, 1800, 2100 and 2700 μg mL^-1, respectively, decreased the production of IAA by 19.5 ± 1.9 (61%), 18.1 ± 1.2 (64%), 36.4 ± 3.4 (28%), 13.1 ± 0.8 (74%), 15.6 ± 1.0 (69%), 7.6 ± 0.5 (83%), 11.9 ± 0.8 (76%), 24.7 ± 1.7 (51%) and 32 ± 2.3 (37%) μg mL^-1, respectively, over control (50.7 ± 3.6 μg mL^-1). A maximum reduction of 8.4 ± 1.2 (46%), 5.8 ± 0.6 (62%) and 4 ± 0.2 (74%) μg mL^-1 in 2, 3-DHBA at 300 (1×), 600 (2×) and 900 (3×) μg mL^-1 glyphosate, respectively, While, 32.8 ± 2.7 (19%), 27.2 ± 2 (33%) and 21.5 ± 1.3 (47%) μg mL^-1, respectively in the production of SA was observed at 300 (1×), 600 (2×) and 900 (3×) μg mL^-1 atrazine, respectively. Likewise, with increase in concentration of pesticides, decrease in P solubilization ability and change in pH of broth was detected. The order of pesticide toxicity to PSE (percent decline over control) at highest concentration was: atrazine (45) > kitazin (44) > metalaxyl (43) > monocrotophos (43) > glyphosate (41) > hexaconazole (39) > quizalofop (33) > imidacloprid (31) > fipronil (25). The present study undoubtedly suggests that even at higher doses of pesticides, A. vinelandii maintained secreting plant growth regulators and this property makes this strain agronomically important microbe for enhancing the growth of plants.

Kitazin-pea interaction: understanding the fungicide induced nodule alteration, cytotoxicity, oxidative damage and toxicity alleviation byRhizobium leguminosarum

Realizing the severity of fungicidal toxicity to legumes and importance of fungicide tolerant rhizobia in legume production, kitazin tolerant (2400 μg mL⁻¹) strain RP1 was recovered from pea nodules and was identified as Rhizobium leguminosarum (accession no. KY940047). R. leguminosarum produced indole acetic acid (80.5 ± 2.5 mL⁻¹), siderophores: salicylic acid (54 ± 7.3 μg mL⁻¹) and 2,3-dihydoxybenzoic acid (31.9 ± 2.7 μg mL⁻¹), α-ketobutyrate (51 ± 3.2 per mg per protein per hour), solubilized insoluble phosphate (29.5 ± 1.8 μg mL⁻¹) and secreted 29.5 + 2.6 μg mL⁻¹ exopolysaccharides, which, however, decreased consistently with gradually increasing kitazin concentrations. Beyond the tolerance level, kitazin caused structural damage and altered membrane integrity of RP1, as revealed under scanning (SEM) and confocal (CLSM) electron microscopy. Phytotoxicity of kitazin to peas was obvious under both in vitro and in vivo conditions. A significant reduction of 23, 68, 57 and 50% in germination, seedling vigor index, plumule length and radicle length was found at 2× kitazin compared to the control. Cellular damage and cytotoxicity induced by kitazin in membrane altered root cells was detected with acridine orange/propidium iodide (AO/PI) and Evans blue dye. A maximum increase of 1.72, 5.2, 9.3 and 1.72, 5.2, 9.3-fold in red and blue fluorescence was quantified at 1×, 2×, and 3× doses of kitazin, respectively. In contrast, application of R. leguminosarum RP1 alleviated toxicity and enhanced the length of plant organs, dry biomass, symbiotic attributes, photosynthetic pigments, nutrient uptake and grain features of peas comparatively uninoculated and fungicide-treated plants. Additionally, strain RP1 expressively reduced the antioxidant enzymes peroxidase, ascorbate peroxidase, guaiacol peroxidase, catalase and malondialdehyde contents by 10, 2.2, 11, 20 and 4% compared to stressed plants raised at 192 μg kg⁻¹ soil. Moreover, a decline of 19, 21 and 20% in proline content extracted from roots, shoots and grains, respectively was recorded for R. leguminosarum inoculated pea plants grown with 96 μg kg⁻¹ kitazin. Also, the SEM and CLSM of roots revealed the bacterial colonization. In conclusion, R. leguminosarum tolerated a higher level of kitazin, secreted plant growth promoting (PGP) bioactive molecules even under fungicide stress and significantly increased the performance of peas while reducing the levels of proline and antioxidant enzymes. So, it can safely be suggested to legume growers that RP1 strain could inexpensively be explored as an efficient biofertilizer for enhancing the production of legumes especially peas while growing even under fungicide (kitazin) enriched soils.

Realizing the severity of fungicidal toxicity to legumes and the importance of fungicide tolerant rhizobia in legume production, kitazin tolerant strain RP1 was recovered from pea nodules and was identified as Rhizobium leguminosarum.

Heteroplasmy for the Cytochrome b Gene in Podosphaera xanthii and its Role in Resistance to QoI Fungicides in Spain

In Spain, management of the cucurbit powdery mildew pathogen Podosphaera xanthii is strongly dependent on chemicals such as quinone outside inhibitor (QoI) fungicides. In a previous report, widespread resistance to QoI fungicides in populations of P. xanthii in south-central Spain was documented, but the molecular mechanisms of resistance remained unclear. In this work, the role of the Rieske-FeS (risp) and the cytochrome b (cytb) gene mutations in QoI resistance of P. xanthii were examined. No point mutations in the risp gene were found in the three QoI-resistant isolates analyzed. For cytb, sequence analysis revealed the presence of a G143A substitution that occurs in many QoI-resistant fungi. This mutation was always detected in QoI-resistant isolates of P. xanthii; however, it was also detected in sensitive isolates. To better understand the role of heteroplasmy for cytb in QoI resistance of P. xanthii, an allele-specific quantitative PCR was developed to quantify the relative abundance of the G143 (sensitive) and A143 (resistant) alleles. High relative abundance of A143 allele (70%) was associated with isolates resistant to QoI fungicides; however, QoI-sensitive isolates also carried the mutated allele in frequencies ranged from 10 to 60%. Our data suggest that G143A mutation in cytb is the primary factor involved in QoI resistance of P. xanthii but the proportion of G143 and A143 alleles in an isolate may determine its QoI resistance level.

Toxicity of fungicides toPisum sativum: a study of oxidative damage, growth suppression, cellular death and morpho-anatomical changes

Considering the fungicidal threat to the sustainable agro-environment, the toxicological impacts of three fungicides, namely kitazin, hexaconazole and carbendazim, on the biological, chemical and morpho-anatomical changes of peas were assessed. Fungicide applications in general caused a slow but gradual reduction in growth, symbiosis and yields of peas, which, however, varied appreciably among species and concentrations of the three fungicides. Of the three fungicides, carbendazim had the most lethal effect, in which it delayed seed germination and also diminished the overall pea growth. Carbendazim at 3000 μg kg⁻¹ maximally reduced the germination, SVI, size of roots and shoots and total dry matter accumulation in roots, shoots and whole plants distinctly by 40%, 84%, 72%, 73%, 68%, 75% and 73% (p ≤ 0.05), respectively. Hexaconazole at 120 μg kg⁻¹ significantly (p ≤ 0.05) declined total chlorophyll, carotenoids, grain yields, grain protein, root P and shoot N by 19%, 28%, 46%, 69%, 48% and 51%, respectively, over the control. The synthesis of stress biomarkers and oxidative stress were increased with increasing dosage rates of fungicides. Proline content in roots, shoots, leaves and grains, MDA, electrolyte leakage and H₂O₂ of plants grown in soil treated with 288 μg kg⁻¹ kitazin were increased significantly (p ≤ 0.05) by 73%, 52%, 41%, 24%, 59%, 40% and 27%, respectively, relative to the control. Antioxidant defence enzymes were greater in pea foliage. The SEM and CLSM images revealed an obvious alteration in root tips, enhanced cellular damage and cell death when plants were raised under fungicide stress. Also, morpho-anatomical variations in fungicide-treated foliage were visible in the SEM images. Overall, the present study suggests that a careful and secure strategy should be adopted before fungicides are chosen for enhancing pulse production in different agro-climatic regions.

Considering the fungicidal threat to the sustainable agro-environment, the toxicological impacts of three fungicides, namely kitazin, hexaconazole and carbendazim, on the biological, chemical and morpho-anatomical changes of peas were assessed.

Synthesis and fungicidal activity of 1,1-diaryl tertiary alcohols

A series of 1,1-diaryl tertiary alcohols and some of their dehydration derivatives were designed, synthesized and evaluated for their antifungal activities. Some compounds exhibited moderate inhibitory activities against seven plant pathogens at 50μg/mL in vitro, compounds 5g and 7c displayed nearly the same or higher fungicidal activities against some certain plant pathogens compared with the lead compound pyrimorph. A qualitative structure-activity relationship (SAR) analysis revealed that the Cl substituent and its position at the pyridine ring were crucial for the compounds' activities. Specially, several compounds displayed 100% protection effect against wheat powdery mildew or cucumber anthrax at 400mg/mL in vivo, which suggested that these compounds might be potential fungicidal candidates for certain plant diseases.

Hydrogen Bonding to the Substrate Is Not Required for Rieske Iron-Sulfur Protein Docking to the Quinol Oxidation Site of Complex III

Complex III or the cytochrome (cyt) bc₁ complex constitutes an integral part of the respiratory chain of most aerobic organisms and of the photosynthetic apparatus of anoxygenic purple bacteria. The function of cyt bc₁ is to couple the reaction of electron transfer from ubiquinol to cytochrome c to proton pumping across the membrane. Mechanistically, the electron transfer reaction requires docking of its Rieske iron-sulfur protein (ISP) subunit to the quinol oxidation site (Q_P) of the complex. Formation of an H-bond between the ISP and the bound substrate was proposed to mediate the docking. Here we show that the binding of oxazolidinedione-type inhibitors famoxadone, jg144, and fenamidone induces docking of the ISP to the Q_P site in the absence of the H-bond formation both in mitochondrial and bacterial cyt bc₁ complexes, demonstrating that ISP docking is independent of the proposed direct ISP-inhibitor interaction. The binding of oxazolidinedione-type inhibitors to cyt bc₁ of different species reveals a toxophore that appears to interact optimally with residues in the Q_P site. The effect of modifications or additions to the toxophore on the binding to cyt bc₁ from different species could not be predicted from structure-based sequence alignments, as demonstrated by the altered binding mode of famoxadone to bacterial cyt bc₁.

Ametoctradin is a potent Qo site inhibitor of the mitochondrial respiration complex III

Ametoctradin is a new Oomycete-specific fungicide under development by BASF. It is a potent inhibitor of the bc1 complex in mitochondrial respiration. However, its detailed action mechanism remains unknown. In the present work, the binding mode of ametoctradin was first uncovered by integrating molecular docking, MD simulations, and MM/PBSA calculations, which showed that ametoctradin should be a Q(o) site inhibitor of bc1 complex. Subsequently, a series of new 1,2,4-triazolo[1,5-a]pyrimidine derivatives were designed and synthesized to further understand the substituent effects on the 5- and 6-position of 1,2,4-triazolo[1,5-a]pyrimidine. The calculated binding free energies (ΔG(cal)) of newly synthesized analogues as Qo site inhibitors correlated very well (R(2) = 0.96) with their experimental binding free energies (ΔG(exp)). Two compounds (4a and 4c) with higher inhibitory activity against porcine SQR than ametoctradin were successfully identified. The structural and mechanistic insights obtained from the present study will provide a valuable clue for future designing of a new promising bc1 inhibitor.

Discovery of 1,2,4-triazole-1,3-disulfonamides as dual inhibitors of mitochondrial complex II and complex III

1,2,4-Triazole-1,3-disulfonamide derivatives as dual function inhibitors of mitochondrial complex II (SQR) and complex III (cyt bc₁) were discovered.